Is it ok to surface halfway through a dive then go back down?

[Thalassamania]

Many divers are against see-saw profiles as they believe that they increase your odds of getting bent. Some time ago I PM'd Dr Deco about this and (to the best of my recollection) his response was that there was no information to support such a notion. In my opinion the key things are to have a safe ascent and to descend only if you have enough air.

With all respect ot Dr. Deco ... there are a number of well documented cases of "bubble pumping."

I guess the question should be - Does anyone have any direct experience with yo-yoing resulting in DCS?

Not personal experience, but incident reports that I have read (including one that left a residual area of anesthesia on the left thigh of a friend.

I'm not a deco expert but,
I remember reading/watching somewhere that the biggest problem with this after big dives is that it simulates a PFO, allowing bubbles to pass over to the arterial side and lodge in the smaller capillaries.

Correct.

Are you diving tables?

Minimum time surface interval by SSI/NAUI dive tables is 10 minutes. Anything less would be considered part of the same dive.

I would suggest a safety stop unless it was an emergency.

Hope this helps.


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The problem is only partially the surface interval between depth excursions (and 10 min. may not be adequate) but the time spent underwater during the subsequent excursion.

I think the issue with someone going back down for bottles is that you compress the bubbles enough to let them through the pulmonary filter, and then you don't stay down long enough for them to collapse, so they expand greatly on ascent.

If you surface halfway through a dive, spent virtually no time on the surface (peek and go) and return to the depth where you were, it's kind of like the commercial diver who surfaces and walks into a chamber. If you then spend significant time (and do I know how much that is? No way.) at depth, you may well be okay.

I suspect this is something a lot of us have done from time to time -- I try not to make a habit of it, but I have done it with no ill effects.

All true, including the fact that we've all done it with no ill effects ... at least so far.

You mean something like jumpjng in, losing a fin, chasing it down and catching around 35ft then coming back up to put it on and signal all is ok then following up with a standard Cozumel reef dive?

Nope, never done it.
And if I did I am sure I would not had any trouble from it.

The likely problem is in the following window: a longish, deepish excursion followed by a fairly quick ascent with a short surface interval (I'd hipshoot at more than 3 min and less than 10 min), a short re-submergence and finally an ascent (even a rather slow one). This profile is typical of making a dive, surfacing and then diving to clear the anchor (that's where most of the problems I've heard of have occurred).

 

[diver 85]

Divers do goofy things @ different times--yes, you'll survive.......IF----you do(some) things S-L-O-W-L-Y...

 

[String]

I guess the question should be - Does anyone have any direct experience with yo-yoing resulting in DCS?

No but i have 2 friends that have been bent where the chamber has told them it was almost certainly their saw-tooth profile that caused it. They were within computer limits (by a long way). No PFOs or other complicarions. Well hydrated.

 

[aquaregia]

I read a GI3 rant about support divers getting bent after doing final bounce dives to retrieve the 6m tanks.

 

[Wookie]

From a completely different perspective:

Your dive operator won't like it. If you do it, make sure the folks on the boat see you, you give them a big OK, and indicate that you intend to continue your dive. We call coming to the surface and looking for the boat "spyhopping", and it makes us nervous. Not because we're afraid you'll get bent, but bad things happen at the surface. Most divers who get in trouble will get to the surface, turn over, and disappear. Those are the times when we ask ourselves "was the diver in passive panic? Does the diver need help? Is the diver so out of air that he/she can't inflate their BCD?" We're not too worried about you getting bent, but we're scared to death you're going to drown. So, we go into full rescue mode, and you most likely don't want to be rescued, especially when we first get our hands on you.

So, if you're going to do it on a charter boat, give a nice big OK when you surface and a big thumbs down when you go back down so we don't have a fit.

 

[Kingpatzer]

I've done it too. But I always have made sure at the end of the dive I spent some time talking to my buddy about our failure to either (a) properly plan the dive or (b) properly navigate or (c) both. Figuring out what went wrong, learning from that experience, and trying to apply those lessons to future diving will minimize those events.

 

[HowardE]

Also... in some places, they suggest you DO surface mid dive to check on the boat position.

 

[MauiScubaSteve]

Reefs in Key Largo are difficult to navigate, peek and see is a common practice though depths are generally very shallow.

agreed :cool2:

 

[Charlie99]

Also... in some places, they suggest you DO surface mid dive to check on the boat position.

Many Florida Keys boats make that recommendation. I invariably ignore it.

OTOH, I'd do it if I weren't sure of my position. Weighing the risk of a boat check mid dive on a typical Keys 30' max depth dive vs the risk of ending up downcurrent and lost, mid dive boat check makes a lot of sense.