u-853 penetration

[bell47]

You guys that have gone through the u-853 do you suggest going bow to stern or stern to bow? Bow meaning the blast hole just forward of the conning tower and stern meaning the blast hole, well, back at the stern. is there anything to see forward of the forward blast hole or do most guys just go between the holes? Any tricky snaggs, or tight squeezes?

 

[BigHarryDiver]

Me and a couple buddies are scheduled to dive the U-853 at the end of July so I'm very interested to see the responses you receive.

Thanks for posting!

 

[bell47]

Have you been on this wreck before? We dove it last August and it's a good wreck. What charter boat are you guys diving? We used Atlantis Dive charters from New London, and are gonna use them again. Last year we didn't swim through, just barely penetrated the blast holes to look around. This year we want to go through.

 

[Gilldiver]

I wrote this up a few years ago, it should answer many of your questions.

Pete Johnson


The U-853 Part 1

Whenever diving any wreck it is always good to know the wreck before the dive. Some wrecks you can only get a photo off, but others like the U-853 there are a lot more resources. The best is the U-505 at the Museum of Science in Chicago. The 505 is of the same design as the 853 and any trip to her will open your eyes much better then I can to what is in the wreck. But look around and get some sketches of the layout of the boat.

Outside of the U-853

But from bow to stern on deck: The upper part of the bow has fallen off and now lies to the Port side. Be careful it as the sheet metal is thin and very sharp, I have seen parts of it flexing in the current. Looking around about 5’ off the sand you will see the forward torpedo tubes, 3 of the tube doors have been opened. If you look in the upper left hand tube, you will see the remains of one of the torpedoes. A little further back at sand level are the forward diving planes. Back up top and working back you will find the windless and forward torpedo loading hatch. This hatch is about 22” in diameter and is the largest hatch into the sub. As you head back, the upper portion of the pressure hull is all that remains as the decking has all corroded away. The next “hatch” that you will find is a rectangular hatch. This is the battery loading hatch and was never opened at sea. Smaller divers can get through it with some effort, but I would need to take my tanks off. About 10-15 feet aft of the battery hatch is the forward crew hatch into the crews quarters. A small diver can get through with tanks on, but it helps if you have someone to help, and you need to be "clean," no canister lights, stage bottles, reels etc. to clutter up your chest or sides.

Don’t be looking for a large deck gun like you see in all the movies. The Type IX had a 105 mm gun at the beginning of the war but all had them removed by the end of 1943. The largest gun the U-853 had at the time of sinking was a 37mm anti-aircraft gun which was located aft of the conning tower.

As you head further back you will find the forward “bomb” hole. This is the area directly over the captain’s cabin, sound and radio rooms which are long gone. A quick drop into the hole and you will find the round hatch into the control room. This hatch is about 30” wide and easily penetrated – more on penetration later. Looking forward in the bomb hole you will see hull plating bent down to your right and if you look to the left you can see access into the forward crews quarters.

Just as you come out of the bomb hole look on the right side of the wreck and you will see a long “pipe.” This pipe is the snorkel in the retracted position. The air head is at the end away from the conning tower. Just aft of the bomb hole is the conning tower. On top you will see a bright silver pipe coming up, this is the remains of the attack periscope, the actual head was cut off back in the 60’s or 70’s. The next pipe back is the search periscope in its retracted position. All you see is the periscope head as the lens is long gone. In front of the periscopes is a small hatch into the conning tower. This hatch is the smallest hatch on the boat and few have gone through it.

Aft of the conning tower is the mount for the 37mm AA gun. Further aft is a hatch into the engine room. Next, aft on the right side of the wreck is a bomb hole into the electric motor room, you will need to drop over the side to find it. The hole is large enough to get through easily, but watch out for the sharp sides.

Heading further aft you will find the aft torpedo loading hatch and the remains of the after torpedo room. The top hull plating is blasted away and you can drop right down into it with plenty of room to look around. Looking forward is a round hatch into the Electric motor room. On most days looking through this hatch you will see the bomb hole on the right side and if you have to be “inside” the sub, this is the best straight through of about 15 feet, in the hatch and out the bomb hole. Looking aft you will see more hull plates blasted down and if you look behind them you will see the tops of two parallel horizontal tubes, these are the two aft torpedo tubes. You can now exit straight up through the bomb hole or out the left hand side of the wreck at sand level and have a look at the remains of the propeller shafts and steering mechanisms and rudders/dive planes.

U-853 a Type IX German U-boat by compartment

From the front of the sub to the back. Any descriptions as to left or right will be in relation to the diver, not the actual right (starboard) or left (port) side of the sub. The directions will be for a diver moving from forward to the stern unless otherwise noted.

Compartments
Forward Torpedo Room
Crews Quarters, Captains Cabin, Radio & Sound Rooms
Control Room
Conning Tower (above the control room)
Diesel Engine Room
Electric Motor Room
After Torpedo Room

Some things to Think About. This is a War Grave, there are human remains in the forward torpedo room, crews quarters, and control room that may be on the surface and easily seen. Proper respect for these remains should be shown at all times. In other words, leave them alone. look but don’t play with any bones as they are the remains of men who did their best for their country.

All the rooms are tight and it is almost imposable not to stir up the bottom. The good news is that a lot of the sand and silt is really sand and shell and doesn’t come up without a bit of effort. But it will cloud out and there is always the possibility that another diver has been in the room to mess things up for you. I highly recommend that no one new to the wreck penetrate the sub without a buddy who knows it and has many dives on it.

Forward Torpedo Room. There are only two ways in to this room. The first and best is through the torpedo loading hatch. I am 6’3” and with twin 100’s and a dry suit I can get through the hatch. But you need to clean up – remove any reels, stage bottles, etc and hold them in front of you. A small canister light on your belt strap should be OK but you may need to guide it a bit. Once through, clip everything back on. You should be on some firm sand and shell facing forward and may see the round disk of the hatch to the after compartments right next to you. If you see a round hatch combing right in front of you on a bulkhead, you are facing aft, turn around. A bit forward and to your left is the remains of a torpedo, (please don’t play with it, I may be in the water if it goes off). On the overhead in front of you, you will see two I-beams, these were for supporting the torpedoes as they were loaded into the tubes. They are your guides in any silt out. If you are silted out, stop, feel upward and find these I-beams, they are the highway out. At one end are the torpedo tubes at the other end are the hatches, if you hit the tubes, turn around and follow them back to the hatches.

As you move forward the sand and shell change to light silt, so be careful and maintain your buoyancy and keep the dangles out of the silt. At the torpedo tubes you will find that the two lower tubes are covered over with sand/silt, but the two upper ones are visible. The right hand side tube has had its door opened; the left hand tube is still closed (and loaded). By now rust and silt that have been stirred up by you and your bubbles will start clouding around you, it is time to move back aft. Remember to use the I-beams if there is a lot of silt and if you ran a line, keep it tight and reel it back up so it doesn’t become an entanglement for the next guy.

Back at the hatches you can exit out the torpedo loading hatch or go through the round bulkhead hatch into the crews quarters. To get out the loading hatch gather all your stuff into your hands and keep it all in front of you and “launch” up into the opening and onto the deck.

Crews Quarters. If you go through the round hatch into crews quarters the entries and exit are the hatch from the forward torpedo room, the square battery loading hatch, a round crew accesses hatch, and the forward bomb hole. I have never used the square or round hatches as the bomb hole is just so much easier.

As you enter the crews quarters from the torpedo room you will be in an area with a lot of silt that can be stirred up easily. There will also be the largest number of human remains which will be long arm and leg bones and a few skulls etc. This area can get spooky especially if you are a bit narced, be ready for it. As you head aft try to keep over to your right to get by some vertical supports from the old bulkheads which have rusted away About this time you will be under the square hatch and should be able to see the green glow of the light outside. A littler further aft you will be at the first bulkhead, look to your left and you should see a cubby that is the ships kitchen. If you look closely you will see the electrical elements of the cook top. Go through the remains of the bulkhead hatch, which is rectangular and not round, and you will be in officer’s country. This is where the executive officer and senior petty officers were. In this area you will be under the round hatch and should see the green glow of it if you look up. Keep to the right side as you move aft so that you can get around the hull plating that is blown down from when she was sunk. As soon as you are past the plating you will have an unobstructed exit out of the sub through the forward bomb hole. The area where the bomb hole is was the captain quarters (right side), radio and sound rooms (left side) were. In the bomb hole looking aft you will see the round hatch into the control room.

Control Room. Looking aft while in the bomb hole you will see the large round hatch that leads into the sub’s control room, this was the operational heart of the boat. There are 3 ways into the control room, the first is the large round hatch from the crews quarters and the forward bomb hole, the next is a large round hatch in the aft bulkhead leading into the diesel engine room and the third is a small hatch that leads into the conning tower. The hatch to the conning tower is very tight and no diver can get through it with tanks on. It should never be considered to be an escape route, 1st because it is so tight, 2nd because it leads to another compartment that is even more difficult to get out of.

As you enter the control room, just in front and slightly to your right will be a mound. This mound is the remains of 37 mm antiaircraft ammunition. The cases were steel and have mostly rotted away. You will still find the shells or bullets, but don’t play with them. They are explosive shells and still live, also some are tracer rounds have phosphorous in them and might light off if exposed to air.

Hard to your left is the planesmen’s stations. There used to be large steel wheels there but they have rusted away. A bit further in and slightly to the left of the boats centerline is a large column which is the casing for the two periscopes. There is a small access door on the front side that you can try to have a look through. Immediately in front of the periscope support is the combing of the hatch into the Conning Tower (more on this later). Take your time and look around here, there is a lot to see. As in any wreck, look up – almost all divers only look down and so miss ½ of the wreck. If you plan to go further aft in the control room or on into the diesel engine room, keep to the right to pass around the periscope support. A very small diver might get around to the left of the support, but only at great effort and the complete stirring up of the silt/sand.

Once past the periscope support you should see a number of valves in the far right corner and a large round hatch leading into the diesel engine room.

 

[Gilldiver]

The U-853 Part 2

Conning Tower. I really can’t tell you much about the Conning tower as I have never been in it (or the conning towers of the U-85 or U-352). Nor have many others. The two hatches into the Conning tower are: 1) The hatch from outside on top that you should have seen on your swim around the outside and 2) The hatch down into the Control room. As you will find, both hatches are only about 20-24 inches wide. The divers that have been inside the Conning tower have reported it very tight with the periscopes taking up almost all the room just aft of the entry. The divers I know tell me that there was only room to turn around in. Please note, these divers took their tanks and fins off and had support divers to help them in and out. In all cases the diver penetrating the Conning tower used a 30 or 40 pony/stage for the penetration part of the dive. An experienced team of wreck divers should have at least 3 divers – the penetration diver, one to help the penetration diver into and out of his tanks (and fins, the amount of movement to get through the hatch with fins on would completely spoil the vis inside), and one to aid the penetration diver into and out of the hatch and hand in/out any camera/video units. The conning tower is no place for any diver who A) does not have years of experience and B) a support team dedicated to his/her safe entry and exit.

The interactive video on the U-505 site referenced earlier will give you a much better picture of what is in the Conning tower then I can.

Diesel Engine and Electric Motor Rooms. If you decide to penetrate into the diesel engine room, you will be entering one of the tighter and furthest away compartments of the wreck. Once inside you will have to pass through one compartment and at least one hatch to reach an easy exit both ways. The area between the diesel engines is also the tightest passage that you will have to do in the boat.

There are three exits in the diesel engine room, the round hatch from the control room, a rectangular hatch into the electric motor room, and a crews hatch to the outside that is at the forward end of the diesel engines. This hatch will exit next to the 37mm anti-aircraft mount on the exterior of the boat. It is tight, larger divers and almost all divers with dry suits will have to take their tanks off to get through it.

As you enter the diesel engine room, you will be in one of the larger areas in the room. In front of you are the two engines and right above you are the main induction valves that let in air to run the engines on the surface or when using the snorkel. To your right you may see some white round objects on the floor, these are glass electrical fuses. If you look carefully at the front of the engines you may be able to see the remains of the start/stop and throttle stations. But these stations are much deteriorated. On top of the engines you will see the valve rocker arms and springs. A good viewing of the movie Das Boat (The Boat) will go a long way in helping you visualize this area, even if the boat in that movie was a Type VII.

About 4 or 5 feet past the very front of the engines and above them is the crews hatch to the outside. The hatch is tight, but smaller divers can make it out with tanks on, but only with effort and there is a combing of about 20” that you have to pass through. All of the other hatches on the boat are thin in section and once you pass the thickness of the hull you are done. This hatch is more like a short tunnel. When passing between the engines you only have about 24” of clearance between the engine blocks, it is tight. Take careful notice of the diesel fuel feed lines that run the length of the engines right where you want to go. I find that I have to keep my shoulders above these lines to pass through. The good news is that they do make good hand rails to pull yourself along with.

When you have passed the engines you will be in a larger area where you can stop and have a good look at the back of the engines. On the bulkhead right in front of you facing aft is the rectangular hatch, or really a door, to the Electric motor room. Passing through this hatch is fairly easy, but I find getting my arms and shoulders through first and pulling through works well. You are now in the Electric Motor Room.

Electric Motor Room. As the name implies, this is where the electric motors are. This compartment has 3 exits, the rectangular hatch to the Diesel Engine Room, a round hatch into the After Torpedo Room, and a large bomb hole on the Starboard side aft (the diver left side heading aft) in the compartment. The electric motors were used when the boat was submerged. The motors themselves are mostly under the decking as they were directly attached to the propeller shaft, but you can see the curve of the top of both of them. This compartment is perhaps the easiest and most “clean” of all the intact compartments and easiest to penetrate. Besides the top of the motors, there is not a lot to see, but as it is clean. The bomb hole is big enough to easily get though, but you need to take care os the edges which can be sharp. Other then the large bomb hole forward of the conning tower, this is the easiest entry into an intact compartment on the wreck.

I would recommend that newer divers spend some time in here just looking around, let the sound track of Das Boat play in your head, and perhaps say a prayer for the crew who still remain on the boat. Most were less then 22 years old and most knew that by that time in the war, they were on a suicide mission, but went anyway and died for their country.

Penetration dives of the wreck.

I want to go over some easy penetrations and how you might want to work up to them. But most important, it will greatly speed your practical education if you can find a good boat and a diving mentor who will show you the ropes, and the wreck.
I’m not going to go over the After Torpedo Room in any depth as I think I did that well enough in the 1st post. Here I’m going to talk about penetration routes.

#1) The easiest route is from the open after torpedo room forward through the large round bulkhead hatch into the Electric Motor room, then out the bomb hole on the wrecks right hand side. You can go forward and have a look through the rectangular hatch into the Diesel Engine room, but don’t go in on your first trip, just get used to the insides of the boat. You may want to do a few entries and exits on this route to get used to passing through the hatch.

#2) A simple in and out of the control room through the forward bomb hole and the round hatch in the control rooms forward bulkhead. Just go in and stop and look around, study the photo’s from the U-505 and try to superimposed your mental image on what you see. After a while, the wreck will start to come alive for you. On your second or third time in the control room, work your way to the after hatch into the Diesel Engine room, then back out through the control room and forward bomb hole.

#3) You should now be comfortable in both the Control room and the Electric motor room, time to put them together. Pass through the Control room and into the Diesel engine room, move slowly and work your way between the engines and back to the hatch into the Electric motor room. Then out the aft bomb hole or through the hatch to the after torpedo room. I find that it is easier to go from the control room aft then to work forward from the electric motor room.

#4) Move forward from the forward bomb hole into the crews spaces. Don’t go far and don’t go past the galley. Just get used to the space and what is there. Then turn around and back out the bomb hole.

#5) If you want to go into the forward torpedo room, practice going through the after torpedo loading hatch. The hatch just leads to the open areas of the after torpedo room, so it is almost like jumping through a hoop. Get used to getting into the area from on deck and from the room area back out through the hatch. When you are both proficient and comfortable doing this, you should be ready for the forward torpedo room. If you go into the forward torpedo room, remember the I-beams are your highway, use them if you are at all unsure.

#6) If you are comfortable in the forward torpedo room, perhaps it is time to head aft into the crews quarters. But don’t do it just to do it and don’t let anyone push you to do it. Many, if not most divers will never go into the forward torpedo room, and even fewer will head aft into the crews quarters. For this route, it is in the forward torpedo loading hatch, back through the crews quarters, past the galley, and on to the forward bomb hole.

#7) The grand tour, In the forward torpedo loading hatch up to the forward torpedo tubes, back into the crews quarters, to the bomb hole, into the control room, then the diesel engine room, on to the electric motor room, and out the after torpedo room. This final dive takes me about 15 minutes to slowly make my way and not stirring up the bottom passing through 7 hatches along the way.

I have specifically not gone into gear, equipment, gasses, tanks, running lines, etc. These are for you to decide on with your training and practical experience. But I would make an observation about lines in the wreck. Just about all the routes I have laid out go in one hatch or area and out another. If you run a line, you will either have to reverse your full trip to reel it up or cut it off. Cutting off a penetration line is not only bad form as far as littering the wreck, but you have just left an entanglement hazard for the next diver/team. For this reason, I do not run a line inside the U-853.

Pete Johnson

 

[bell47]

All I can say is WOW! Thank you for taking the time to give us such a detailed description of the wreck. I really appreciate the info. I'll post back in about a month and let you know what we did. Thanks again, Bell47.

 

[knowone]

AMAZING. So did you dive it?

 

[AfterDark]

Thanks Gilldiver that's a keeper!

 

[keithdiver]

The U-853 Part 2

Conning Tower. I really can’t tell you much about the Conning tower as I have never been in it (or the conning towers of the U-85 or U-352). Nor have many others. The two hatches into the Conning tower are: 1) The hatch from outside on top that you should have seen on your swim around the outside and 2) The hatch down into the Control room. As you will find, both hatches are only about 20-24 inches wide. The divers that have been inside the Conning tower have reported it very tight with the periscopes taking up almost all the room just aft of the entry. The divers I know tell me that there was only room to turn around in. Please note, these divers took their tanks and fins off and had support divers to help them in and out. In all cases the diver penetrating the Conning tower used a 30 or 40 pony/stage for the penetration part of the dive. An experienced team of wreck divers should have at least 3 divers – the penetration diver, one to help the penetration diver into and out of his tanks (and fins, the amount of movement to get through the hatch with fins on would completely spoil the vis inside), and one to aid the penetration diver into and out of the hatch and hand in/out any camera/video units. The conning tower is no place for any diver who A) does not have years of experience and B) a support team dedicated to his/her safe entry and exit.

The interactive video on the U-505 site referenced earlier will give you a much better picture of what is in the Conning tower then I can.

Diesel Engine and Electric Motor Rooms. If you decide to penetrate into the diesel engine room, you will be entering one of the tighter and furthest away compartments of the wreck. Once inside you will have to pass through one compartment and at least one hatch to reach an easy exit both ways. The area between the diesel engines is also the tightest passage that you will have to do in the boat.

There are three exits in the diesel engine room, the round hatch from the control room, a rectangular hatch into the electric motor room, and a crews hatch to the outside that is at the forward end of the diesel engines. This hatch will exit next to the 37mm anti-aircraft mount on the exterior of the boat. It is tight, larger divers and almost all divers with dry suits will have to take their tanks off to get through it.

As you enter the diesel engine room, you will be in one of the larger areas in the room. In front of you are the two engines and right above you are the main induction valves that let in air to run the engines on the surface or when using the snorkel. To your right you may see some white round objects on the floor, these are glass electrical fuses. If you look carefully at the front of the engines you may be able to see the remains of the start/stop and throttle stations. But these stations are much deteriorated. On top of the engines you will see the valve rocker arms and springs. A good viewing of the movie Das Boat (The Boat) will go a long way in helping you visualize this area, even if the boat in that movie was a Type VII.

About 4 or 5 feet past the very front of the engines and above them is the crews hatch to the outside. The hatch is tight, but smaller divers can make it out with tanks on, but only with effort and there is a combing of about 20” that you have to pass through. All of the other hatches on the boat are thin in section and once you pass the thickness of the hull you are done. This hatch is more like a short tunnel. When passing between the engines you only have about 24” of clearance between the engine blocks, it is tight. Take careful notice of the diesel fuel feed lines that run the length of the engines right where you want to go. I find that I have to keep my shoulders above these lines to pass through. The good news is that they do make good hand rails to pull yourself along with.

When you have passed the engines you will be in a larger area where you can stop and have a good look at the back of the engines. On the bulkhead right in front of you facing aft is the rectangular hatch, or really a door, to the Electric motor room. Passing through this hatch is fairly easy, but I find getting my arms and shoulders through first and pulling through works well. You are now in the Electric Motor Room.

Electric Motor Room. As the name implies, this is where the electric motors are. This compartment has 3 exits, the rectangular hatch to the Diesel Engine Room, a round hatch into the After Torpedo Room, and a large bomb hole on the Starboard side aft (the diver left side heading aft) in the compartment. The electric motors were used when the boat was submerged. The motors themselves are mostly under the decking as they were directly attached to the propeller shaft, but you can see the curve of the top of both of them. This compartment is perhaps the easiest and most “clean” of all the intact compartments and easiest to penetrate. Besides the top of the motors, there is not a lot to see, but as it is clean. The bomb hole is big enough to easily get though, but you need to take care os the edges which can be sharp. Other then the large bomb hole forward of the conning tower, this is the easiest entry into an intact compartment on the wreck.

I would recommend that newer divers spend some time in here just looking around, let the sound track of Das Boat play in your head, and perhaps say a prayer for the crew who still remain on the boat. Most were less then 22 years old and most knew that by that time in the war, they were on a suicide mission, but went anyway and died for their country.

Penetration dives of the wreck.

I want to go over some easy penetrations and how you might want to work up to them. But most important, it will greatly speed your practical education if you can find a good boat and a diving mentor who will show you the ropes, and the wreck.
I’m not going to go over the After Torpedo Room in any depth as I think I did that well enough in the 1st post. Here I’m going to talk about penetration routes.

#1) The easiest route is from the open after torpedo room forward through the large round bulkhead hatch into the Electric Motor room, then out the bomb hole on the wrecks right hand side. You can go forward and have a look through the rectangular hatch into the Diesel Engine room, but don’t go in on your first trip, just get used to the insides of the boat. You may want to do a few entries and exits on this route to get used to passing through the hatch.

#2) A simple in and out of the control room through the forward bomb hole and the round hatch in the control rooms forward bulkhead. Just go in and stop and look around, study the photo’s from the U-505 and try to superimposed your mental image on what you see. After a while, the wreck will start to come alive for you. On your second or third time in the control room, work your way to the after hatch into the Diesel Engine room, then back out through the control room and forward bomb hole.

#3) You should now be comfortable in both the Control room and the Electric motor room, time to put them together. Pass through the Control room and into the Diesel engine room, move slowly and work your way between the engines and back to the hatch into the Electric motor room. Then out the aft bomb hole or through the hatch to the after torpedo room. I find that it is easier to go from the control room aft then to work forward from the electric motor room.

#4) Move forward from the forward bomb hole into the crews spaces. Don’t go far and don’t go past the galley. Just get used to the space and what is there. Then turn around and back out the bomb hole.

#5) If you want to go into the forward torpedo room, practice going through the after torpedo loading hatch. The hatch just leads to the open areas of the after torpedo room, so it is almost like jumping through a hoop. Get used to getting into the area from on deck and from the room area back out through the hatch. When you are both proficient and comfortable doing this, you should be ready for the forward torpedo room. If you go into the forward torpedo room, remember the I-beams are your highway, use them if you are at all unsure.

#6) If you are comfortable in the forward torpedo room, perhaps it is time to head aft into the crews quarters. But don’t do it just to do it and don’t let anyone push you to do it. Many, if not most divers will never go into the forward torpedo room, and even fewer will head aft into the crews quarters. For this route, it is in the forward torpedo loading hatch, back through the crews quarters, past the galley, and on to the forward bomb hole.

#7) The grand tour, In the forward torpedo loading hatch up to the forward torpedo tubes, back into the crews quarters, to the bomb hole, into the control room, then the diesel engine room, on to the electric motor room, and out the after torpedo room. This final dive takes me about 15 minutes to slowly make my way and not stirring up the bottom passing through 7 hatches along the way.

I have specifically not gone into gear, equipment, gasses, tanks, running lines, etc. These are for you to decide on with your training and practical experience. But I would make an observation about lines in the wreck. Just about all the routes I have laid out go in one hatch or area and out another. If you run a line, you will either have to reverse your full trip to reel it up or cut it off. Cutting off a penetration line is not only bad form as far as littering the wreck, but you have just left an entanglement hazard for the next diver/team. For this reason, I do not run a line inside the U-853.

Pete Johnson

Thank you very much Pete for your deligent effort in explaining the wreck .

 

[Gilldiver]

AMAZING. So did you dive it?

Well, the forward upper Port torpedo tube might look like this:

Take a good look at the bottom of the photo, you will see the very fine silt that has gathered at the forward end of the forward torpedo room. This stuff comes up real fast.