"Deco" in current

[LCF]

This is probably a very stupid question, but I'm going to ask it anyway, because this site seems to have a lot of people who dive wrecks.

On the trip to the BVI from which I just returned, we did a number of dives on wrecks. In each case, the boat was tied in to a buoy line, and we needed to ascend at the boat. On one dive, the current was so strong, there was no question how to do the ascent -- we ALL went hand over hand up the buoy line. (I was powerfully reminded of the "Why DIR" video as we did this ) But on a couple of the other dives, there was variable current, or a current present shallow that wasn't a problem deep. In a couple of cases, my team, doing what was otherwise a beautiful ascent with minimum deco, ended up an annoying distance from the boat when we surfaced.

My question is: What does a well-trained DIR diver do in such cases? Do you just try to swim against the current to stay in sight of the upline? Do you use a jon line or something similar, so that you can stay horizontal and in trim, but not exert yourself unduly while trying to maintain position wrt the boat? Do you just drift and do the surface swim? Or do you just give up and grab the upline like everybody else?

[Mark Chase]

Obviously I am not fully DIR but a few points for you to consider...

Surley this is a diving logistics issue? Plan the dive. Ask the skipper of the boat what he needs you to do and have the necessary equipment ready to do it. This may include a 125m reel for bagging up from depth and it may necessitate full deco on 50% as it will not be possible to use 100% and an ascent up the line.

This is a very common problem when diving in the English Chanel especially in the area of Ramesgate and Dover. The currents are very very strong, slack windows are often 30mins or less and the enormous amount of shipping in the area makes it like surfacing in the middle of a motorway.

There is only one way to ascend near the shipping lanes and its hand over hand up the shot line. The currents can be so strong that holding the shot for any length of time is very uncomfortable so John lines are a good idea.

The other problem you will suffer is the use of 100% for deco. With 10 -12 divers on the line your often unable to get to 6m. I have had to deco out at 9m due to 10 divers above me all trying to be at 6.

Finally, doing shallow SMB deployments when drift deco is possible, can be problematic. The skipper needs to know that all divers are on the bag before he pulls the shot from the wreck and follows the SMB's As a result they prefer the SMBs sent up from the wreck. Wrecks down to 60m we send up an SMB from the wreck. Wrecks deeper than that we use a lazy shot deco station and all return to that.

There are areas of English water where it is possible to free ascend and we do get good slow running neaps which allow it as well. However if divers are spending 120min+ in the water you can almost guarantee ascending in a big ish to big current.

Being able to do a free ascent is a good skill and all decompression divers should be capable of it. However doing it on every dive is not necessarily viable.

ATB

Mark Chase

[Brian Allen]

Quote: (Originally Posted by LCF)

My question is: What does a well-trained DIR diver do in such cases? Do you just try to swim against the current to stay in sight of the upline? Do you use a jon line or something similar, so that you can stay horizontal and in trim, but not exert yourself unduly while trying to maintain position wrt the boat? Do you just drift and do the surface swim? Or do you just give up and grab the upline like everybody else?

I'd use a skipper that his happy to use a chase boat or pick me up. Drift deco, nice n easy, and when i surface theres a boat there that's been following the marker buoy.

B

[Bob Cooper]

Quote: (Originally Posted by LCF)

My question is: What does a well-trained DIR diver do in such cases? Do you just try to swim against the current to stay in sight of the upline? Do you use a jon line or something similar, so that you can stay horizontal and in trim, but not exert yourself unduly while trying to maintain position wrt the boat? Do you just drift and do the surface swim? Or do you just give up and grab the upline like everybody else?

Simple answer is that we don't do it (ascend a fixed shot in a current).

The boat is never tied to the wreck. The divers and the boat all drift in the current.

[Mark Chase]

Quote: (Originally Posted by Bob Cooper)

Simple answer is that we don't do it (ascend a fixed shot in a current).

The boat is never tied to the wreck. The divers and the boat all drift in the current.

So does this mean a DIR diver would simply not dive a wreck in or near the shipping lanes off Dover for example? Bearing in mind a diver in Dover ascending on an SMB was hit by a large tug boat last year suffering multiple injuries, doesn't it seem safer to do a fixed line ascent?

As an aside the boat is never tied into the wreck the ascent line is connected to an independent buoy which is protected by the boat. It is much easier for the boat to protect a buoy with 12 divers under it than it is to protect 12 divers spread out over 1/2 a mile of sea.

I am pretty sure if you look at the GUE site for the Britannic dives you will find divers ascending a permanent shot line. So if JJ and the other two disavowed DIR divers AG and Barry can do it, you probably can too.

The divers I dive with would consider it reckless to do a free ascent or SMB drift on 3 hour dives so most of our deep diving is done using a deco station and shot line ascent regardless of shipping lanes and drift conditions. Its felt that having the whole team together on the station also adds safety to the dive in the event something should go wrong.

Mind you that could just be an excuse as some prefer to clip off to the station and just fall asleep :D


ATB

Mark Chase

[LCF]

Well, maybe this wasn't such a stupid question after all . . . Am I reading you right, Bob, that in your view only diving with a live boat pickup is DIR? That would certainly let out diving off a great many commercial dive operations in various places.

[Bob Cooper]

Quote: (Originally Posted by Mark Chase)

So does this mean a DIR diver would simply not dive a wreck in or near the shipping lanes off Dover for example?

No, it just means we would do it drifting. As you know we have done hundreds of these sort of dives without any issues.

Quote: (Originally Posted by Mark Chase)

Bearing in mind a diver in Dover ascending on an SMB was hit by a large tug boat last year suffering multiple injuries, doesn't it seem safer to do a fixed line ascent?

That was a one-off and would have still happened if there were a dozen divers on a fixed line. I also seem to remember the same thing happened to you one time when an Orange boat got messed up in your station?

Quote: (Originally Posted by Mark Chase)

It is much easier for the boat to protect a buoy with 12 divers under it than it is to protect 12 divers spread out over 1/2 a mile of sea.

The reality of this is very different from the theory. In reality the divers are never 1/2 a mile apart, more like about 10m apart. On most of our dives we will see the other teams doing their drifting deco on ascent. Sometimes, we swim over to them just to say hello :-)

Quote: (Originally Posted by Mark Chase)

I am pretty sure if you look at the GUE site for the Britannic dives you will find divers ascending a permanent shot line. So if JJ and the other two disavowed DIR divers AG and Barry can do it, you probably can too.

I don't know too much about the logistics of the Brittanic dives, but I do know they made use of scooters which puts a different dimension on the logistics of doing fixed line deco.

Quote: (Originally Posted by Mark Chase)

The divers I dive with would consider it reckless to do a free ascent or SMB drift on 3 hour dives

Again, as you know, we don't do 3 hour dives in the ocean.

[Bob Cooper]

Quote: (Originally Posted by LCF)

Well, maybe this wasn't such a stupid question after all . . . Am I reading you right, Bob, that in your view only diving with a live boat pickup is DIR? That would certainly let out diving off a great many commercial dive operations in various places.

We come up against this one regularly. With our diving (English Channel), we don't have a boat fixed. The boat is free and the divers are drifting when doing their deco.

I have done some of these fixed line ascent dives in a current, mostly on a station and am not happy with them.

On a fixed line, how do you gas switch? How do you maintain buddy contact? How do you verify your buddy has switched to the correct gas? How do you do this in a team of 3? It's bad enough in a team of 2.

If you can't constantly monitor your buddy/team. If you can't verify gas switches and if you can't maintain proper contact - it isn't DIR.

If, during a gas switch, a team member lets go of the line and gets swept away by the current, what do you do? Do you stay on the line? Do you go with him? Then what?

I'm sorry but none of this is DIR in my opinion. I like to be facing my buddy and diving as a team, not hanging on some line like a flag!

I agree that there are many dive operations around the world that use a fixed line but I, personally would not advocate this practice.

Hope that helps

Bob

[Devon Rob]

I never cease to be amazed at how strong a current I can swim against in a relaxed state as long as my kit is tidy and my trim up to scratch!
BUT if I have a long hang in front of me or I feel the exertion is ballsing up my Decompression, I bag off. This is always agreed with the Skipper before the dive. If he´s not prepared or equipped to follow the divers then I adjust my dives to fit, ie. shorter and shallower.

For Expedition dives running 8 Knots in the busiest shipping lane of the world I would still probably not plan for my deco to be done hand over hand on the shot line. My personal experience of rigs/stations is not good, they tend to work well in theory but you need a very skilled group of divers to make them work as they should. Just my tuppence worth.

@LCF I take it the BVI are the Virgin Islands, took me ages to work it out!

[LCF]

Yes, it's the British Virgin Islands, and obviously, none of these dives involved true deco or gas switches. But they did involve current, and as we were not diving off a dedicated dive boat, the boat WAS moored to a buoy during our dives. It was annoying to do a really lovely ascent (for us DIR fledglings) and then have to swim a hundred yards or so in chop to get to the boat. But if I am reading Bob correctly, we did what we ought, which was keep the team together and in good contact and let ourselves drift.