Search and Recovery question! Objects moving underwater.

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dytis-sm

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Location
Santa Monica, CA
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I will be conducting a search and recovery dive for a GoPro lost during a dive. I have a good idea of where it was dropped and I am sure that it was heavy enough to get to the bottom since it was attached to an aluminum pole. The camera was dropped about a week ago on the bottom of Isthmus reef and at about 25 ft of water. That is at a top of a reef surrounded by drops to around 80-100 ft. The terrain is rocky and typical Catalina structure.

I was wondering how strong are currents on the bottom at this area? Shall I be looking at a larger area after the item was sitting on the bottom for a week. I suppose currents are random but do they stir the bottom enough to move an object like this over a period of a week? I am just wondering.

This is not about the camera but more of a thrill and an excuse to dive that area again... I know it is a long shot but wanted to plan the search area. Any recommendations?
 
Keep in mind that it might well not go straight down. I watched a dive pocket fall from somebody going up an anchor line. The pocket fluttered going down and it was going at least 45 degrees from vertical. Boat was out over sand. Pocket landed on the wreck.
 
Don't forget the weather associated with all the rain we've had since it went down. The longer you wait, the more likely it's moved. Do you have GPS coordinates from where you were anchored last weekend so you have a reasonable starting point? You going back this coming weekend?

If you've got a very good idea where he dropped it, try an expanding circle search pattern with someone holding one end of a line (e.g., from a spool) while you swim the search pattern

Wasn't Isthmus reef where a diver got swept away opening night of lobster season this year?
 
Don't forget another diver might have found it already :). Merry X-mas.

I doubt it. This week weather was nusty for diving and we only dropped it last Saturday. I doubt any boats went out there. Plus there is our name and phone number all over the camera so it would be bad karma if one keeps and at least does not try and reach us. Bad Karma from an 11 year old who is pissed as hell ;-)

Geoff, it is not a difficult spot to find although will check with the Captain. The Isthmus reef is in front of the Chamber and the USC Campus but far from shore to do a shore dive. The accident with the anesthesiologist who drowned early in the lobster season was at Emerald Bay which is further up. But there are strong surface currents in the area. This is why I was asking about potential effect on a 25 ft bottom. I suppose it is random but wanted to double check with someone more experienced
 
The camera drifted with the current on its way down so you should start your search where it was dropped then expand the search into the area that was down current that day. If this is an out cropping with a drop off to 80' or 100' on all sides the current at 25' is going to be a lot stronger then the surrounding areas. If the camera hit the bottom at 25' it is probably still where it landed but the current may have carried it far enough to drop it into deeper water. The best way to do the search is with a line running from the diver to a tender on the surface who can monitor and assist your progress. Start your search at one side of the out cropping, swimming at a 90 degree angle to the line, when you reach the other side, signal the surface so the tender can let out some line and then the diver repeats the search swimming in the other direction while still remaining at a 90 degree angle to the line. How much line the tender lets out at each turn will have to determined in advance based on the visibility that day. You can signal the tender with line pull signals, 1 pull from the tender is just asking if you are OK and the diver responds with 1 pull if he is OK, 2 pulls from the diver is a signal to let out line, 3 pulls is a signal to take up line and 4 pulls is a signal to pull the diver up.
 
The camera drifted with the current on its way down so you should start your search where it was dropped then expand the search into the area that was down current that day. If this is an out cropping with a drop off to 80' or 100' on all sides the current at 25' is going to be a lot stronger then the surrounding areas. If the camera hit the bottom at 25' it is probably still where it landed but the current may have carried it far enough to drop it into deeper water. The best way to do the search is with a line running from the diver to a tender on the surface who can monitor and assist your progress. Start your search at one side of the out cropping, swimming at a 90 degree angle to the line, when you reach the other side, signal the surface so the tender can let out some line and then the diver repeats the search swimming in the other direction while still remaining at a 90 degree angle to the line. How much line the tender lets out at each turn will have to determined in advance based on the visibility that day. You can signal the tender with line pull signals, 1 pull from the tender is just asking if you are OK and the diver responds with 1 pull if he is OK, 2 pulls from the diver is a signal to let out line, 3 pulls is a signal to take up line and 4 pulls is a signal to pull the diver up.

Running any kind of pattern from a boat is extremely difficult and inaccurate, unless you have very good visibility. If you have to do a search from a boat, I've found the best way is to tend from the anchor.
 
Running any kind of pattern from a boat is extremely difficult and inaccurate, unless you have very good visibility. If you have to do a search from a boat, I've found the best way is to tend from the anchor.

That would work well if he is anchored on the spot where he dropped it and it did not drift too far. Once you get out of that area this type of pattern becomes less effective. A 25' outcropping surrounded by an 80' drop off it all directions should have a strong enough current to keep the bottom clear of any lose sediment that the diver might kick up so you only need to consider the clarity of the water on that day. Once you know what that is then the tender knows how much line to let out at each turn. If the tender has let out too much line for the diver to see his last pass the diver can signal the tender to take up enough slack to get him into the right position. This pattern works best if you have the boat anchored bow into the current and at least one anchor off the stern so the boat moves from side to side less. Two anchors off the stern, one to port and one to starboard would work better. Using this pattern is more effective at greater distances and will give the tender a much better idea of where the diver has been then the diver himself has. I am making some assumptions here based on what the OP said but if you can tell me what NOAA chart covers this area and give me a GPS location I might be able to give you a more detailed answer to this question.
 
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first I recovered one go pro with out anything except the housing exactly 40 feet below where the owner thought he saw it hit the water. This was after 6 days and some decent currents. The cameras seem to stay put. I would drop a line on the place you lost it. Tie off a reel and start a circle search out from the last point of contact. The size of the circles can be determined by visibility and the number of hidey holes that have to be search. The key is to be methodical don't swim around 1/2 cocked also watch your computer and your pressure gauge do not allow yourself to get task orientated and make a mistake. Remember no go pro is worth that much
just my PSI
Herb
 
Thank you all for your input. Lots of valuable advise.

As one mentioned this is just a GoPro and we already decided it is lost. This is one last shot more like a treasure hunt and a dive excuse ;-) If I find it great, if not, then I had a great search and recovery experience!

Since I am diving off a commercial boat, I cannot have the time or assistance of a tender. Too much overhead and the fellow dives might kill me for taking too much time on one dive. But if the viz is great and there is no surface current I will be doing a surface snorkel around the area. The camera is attached to an extended black pole so it should be visible from the surface on a good viz day. There are also some great landmarks to get direction so between what I remember from the bottom and the landmarks I should be able to find a spot to drop. Then the plan is to do a traditional circular seach using a reel. My reel is 150 feet and I should be able to do a few circles before heading back. I will be diving my 130 cf tank at 25 ft....so I hope my fellow divers do not shoot me when I get back after a couple of hours LOL.

Thanks again on the info.
 

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