Negative Entries - A Bad Idea???

[dirkadirk]

I'm liking a lot of comments here - and see there are views that conflict with my own, which I appreciate as it makes me reconsider my point of view. Thought I'd add a summary of my comprehension, view and a little story.

I've always gone along with the thought that there are 2 types of entry: Positive and Negative.
Positive being air in the BC, and enter the water, even with some height from the take off, i will buoy back up to the surface to conduct checks, find buddy, locate shot line etc.
Negative entries for me are no air in the BC (not sucking it out orally though, just squeezing the elbows back against the plate/cylinder) and entering the water with the intention of not returning to the surface at all, descend to the pre-agreed depth to meet buddy, quick bubble check as we continue descending.

I will always use positive when diving with students, unknown buddies, or on unknown sites (unless specifically briefed against by the dive manager). Negative entries are used when I'm with my regular buddies, on regular dive sites. We usually dive from RHIBs so it makes it easier to just roll back off the tube and continue sinking head first, rather than completing the loop to resurface. It also makes locating my buddy easier as we leave opposite each other so arc round and meet only a couple of metres after entry (think drawing a heart shaped pattern with the boat as the upper trough start point). I also prefer using this when the seas are getting a little bouncy as it means my seasickness doesn't get a chance to play up!! Any time I do a negative entry however I ensure it goes into my plan brief to the Dive Manager and also ensure the Cox'n knows.

Anyway now for my story -

Kids week (local schools send pupils to do OW) at the dive centre I used to work at as a DM. The centre owner deemed it appropriate to steal all bar three of the instructors and all DMs excepting myself and two others, moving them to the sister centre as they had around 50 to our 8. Fair enough, anyways, our freelance instructor bailed at the last moment, as did the two other DMs (real work came around and caught them). We hatched a cunning plan to ensure we all stayed within the Diving at Work regulations, running 3 waves of divers, with us taking longer dives covering 2 training dives each.
Mid week we were doing some bits with shotlines, and some distance lines etc. All entered the water, descended to the bottom at 4m, and found we'd accidentally left the lines on the side. I pop (safely) up and exit the water to collect them. Meanwhile the instructor slowly moved them out to the start of the navigation course under an SMB. Not wanting to surface swim across the harbour I decided to nip out on foot around the harbour wall (much faster) and stride out to drop in.
Tide had lowered a bit so decided that a negative entry would be better given it was approx a 4-5m drop into 12m. All extra gear secured, strode out, a little thrill during the drop.....and then I 'splashed down'. In my haste (my fault of course - less haste more speed) I had clear forgotten to secure my reg and mask with my second hand. No matter, eyes shut, quick windmill to retrieve my reg. Sod the mask, pull out the spare, clear and equalise, and drop some air in the BC for a nice gentle touch down. Quick glance revealed my lost mask right between my knees.

Moral of the story? Negatives are useful and can be fun, especially with a drop; Just don't forget your basic drills!!!

Sorry for what turned out to be War and Peace
Stay Safe and out of Chambers!!

 

[dberry]

I was searching the net for diving speed and stumbled across this instead and thought it was relevant to this thread. It's interesting that dropping weights was not performed or even mentioned in the post accident lessons...

Speed Kills

Note that the article is about a technical diver wearing doubles who jumped in with his valves closed. It's entirely possible he had no weights to drop other than his double tank rig. And as the article mentioned, it's strange he couldn't reach his own valves - skill that is practiced repeatedly as part of the training.

 

[IBjones]

This. I've been instructed to meet up at 30 ft "as soon as possible" after doing backroll entries in Coz, but that was nothing compared to diving a SE Florida wreck in fairly strong current. I'm a newb at this, but I'm still amazed that the Captain could position us so perfectly (un-moored and moving), and that three of us could drop in negative, sink at >99ft/min while moving quite fast horizontally in the current, and still hit spot-on the wheelhouse of the Hydro Atlantic (ca. 130ft) as a group. I know it's "just physics and vector math", but it was still very impressive to me. We did suck the air out of our wings, and especially with doubles there was nothing neutral about the entry The consequences of dawdling on the descent - ending up far down-current of the wreck - would have been painful (as in not diving the wreck.) Obviously the captain and crew were familar with the dive plan. When they said "Dive! Dive! Dive!" they didn't mean "when you feel like it".

Obviously you're a "newb" as you call it.
Around here the boat pulls up to the wreck and one of the crew will dive down and tie the anchor to the wreck. Then the crew deploys what is called a "Carolina rig" (see pic below) that goes from the stern to the bow with weight and a hang tank on it. Once you jump in the water, you hang on the line until your buddy goes it, then you proceed down the anchor line to the wreck casually and safely.

I've never seen this strange procedure where they boat pulls up over the wreck and everyone jumps over and goes balls-to-the-wall to the bottom in order to prevent floating away from the wreck. Kinda odd, not to mention dangerous.

Maybe North Carolina dive operators have just improved on the method.

 

[stuartv]

Obviously you're a "newb" as you call it.

Maybe you just haven't dived anywhere but NC? What he described is called a "hot drop", which typically starts a drift dive to a wreck. Pretty normal in some places. You drop in negative and drop as fast as you can, letting the current carry you to the wreck you're aiming for. The boat basically just hangs around on the surface above the wreck without dropping an anchor or tying into anything. When you're done and ready to ascend, you shoot your SMB and do a free ascent in the current. The boat follows your SMB and picks you up when you hit the surface.

With a hot drop to a deep wreck, the captain has a challenging job to put you in so that you really do hit the wreck, versus being carried past it to one side or the other or not getting down to it and being carried right over it. Getting down as quickly as possible helps the boat captain. The slower you drop, the more chance the current will divert you and you'll miss, or the more chance you'll pass over the wreck and miss it.

 

[IBjones]

Maybe you just haven't dived anywhere but NC? What he described is called a "hot drop", which typically starts a drift dive to a wreck. Pretty normal in some places. You drop in negative and drop as fast as you can, letting the current carry you to the wreck you're aiming for. The boat basically just hangs around on the surface above the wreck without dropping an anchor or tying into anything. When you're done and ready to ascend, you shoot your SMB and do a free ascent in the current. The boat follows your SMB and picks you up when you hit the surface.

With a hot drop to a deep wreck, the captain has a challenging job to put you in so that you really do hit the wreck, versus being carried past it to one side or the other or not getting down to it and being carried right over it. Getting down as quickly as possible helps the boat captain. The slower you drop, the more chance the current will divert you and you'll miss, or the more chance you'll pass over the wreck and miss it.

I won't even go there since NC is the wreck diving capital of North America, and I've dived about all of them in the last 20 years that are recreation-diving depth.

But I haven't drift dived any wrecks so maybe that's the difference.
Sounds like you guys go to a whole lot of extra work by doing it that way. You explained about 5 problems you try to fix by drift diving a wreck that we don't have with regular diving a wreck.

Is that Florida where they dive wrecks like that? I can see where that would be cool in shallow easy water. I've been thinking about going down to there and dive since I have family in St. Augustine and wouldn't have a hotel bill. I thought about taking Amtrak down but I saw on their website their "Homeland security policy" is about like flying on a plane. Too much hassle bringing your own gear. I'd just drive the 10 hours.

We use the Carolina rig, and it works well for us, especially in seas with 8-10 foot swells. You can get an idea of how it works in my video.

 

[dumpsterDiver]

Yes the "hot drop" works well when there is significant surface current. It is much, much more strenuous to pull yourself down and forward fighting the current on an anchor line or any other similar configuration. One advantage to this method is that it is much easier for the captain - all he has to do is sit and wait for the divers to return or to pop up down current. If that occurs he has to chase them down when it is safe to do so. If divers are hanging on the anchor line, he may not be so willing to unhook and leave divers on the line, which presents some safety challenges without a chase boat. It has other logistical advantages as well.

Drifting into and out of the wreck presents some challenges. One of the big limitations of drifting into a wreck in a strong current is the visibility. If the visibility is not good, it makes things much, much harder. It can also be very dangerous if the diver can not see where he is drifting and has some time to avoid obstacles or entanglements, before he is blown directly into them. In a strong current I want a minimum of 30 feet of visibility and where we dive 50 feet is more common - especially when the current is strong. If the site does not have good visibility, drifting into the wreck is not very safe - the work around might be to drop so far up current, that the divers are sure to reach the bottom before any of the wreck and then crawl along the bottom with the current. This presents other problems and makes it very easy to miss the wreck.

I can dive in currents on wrecks that would be impossible to dive by pulling down the line. We don't like it so much, but i have seen surface currents around 4 kts on some of the deeper local wrecks.

Some people may be skeptical about those current speeds; years ago I happened to film some GPS info that shows it.. Skip to 6:05 to see what I am talking about. Typically and thankfully, the current below about 150 feet in our area is generally a lot loss than the surface.

 

[Schwob]

Obviously you're a "newb" as you call it....

Well, for what it's worth:
On two weeks diving off a live aboard in the Red Sea most of our dives off the dinghy were negative entry. Mostly so because of current, sometimes because of other "zippy dinghies"... And no it does not mean being overweighted, just means being negatively buoyant (which you cannot help but being with a full tank when weighted correctly with a mostly empty BCD bladder / wing.

 

[IBjones]

Makes sense. I dive a bit on the rock jetty and it's right in the ship channel near Beaufort Inlet. You get down and get down fast and stay down. Boats come zipping thru there constantly, usually wide open as it isn't a no-wake zone until you get farther up.

I actually surfaced one time a couple decades ago when I was a "newb" and needed to know which way the beach was. First thing I saw was an old geezer in a 20 foot fishing boat about 50 feet away coming right at me. I didn't have time to say "Hi" to him or anything, I just emptied my BC and got back down as fast as I could. Since then I learned to use a compass.

 

[stuartv]

Is that Florida where they dive wrecks like that? I can see where that would be cool in shallow easy water.

My tech instructor did has Adv Trimix training in FL and they did hot drops to hit wrecks that were deeper than 200'. As dd and schwaeble said, I would guess it's because of current. I've dived NC with Discovery and Olympus a few times each and I've never had a dive with either of them where current was anything more than a minor annoyance. Other places, the current can be pretty serious.

 

[tursiops]

My tech instructor did has Adv Trimix training in FL and they did hot drops to hit wrecks that were deeper than 200'. As dd and schwaeble said, I would guess it's because of current. I've dived NC with Discovery and Olympus a few times each and I've never had a dive with either of them where current was anything more than a minor annoyance. Other places, the current can be pretty serious.

I did a dive on the USS Monitor (off NC) once with seriously ripping current. We were using a Carolina rig and it was almost impossible to pull over to the down line. But that was out on the edge of the Gulf Stream.