What happened

[PADI Knight]

Little advice last dive me and my buddy were diving at a fresh water quarry I was ascending from 50 ft jsut below buddy wer were doing a nice gentle slow ascent holding up BC valve to let out air is it expanded. All of a sudden about 20 ft (not sure last check on guage was at 30 ft and several more kicks later) I started to descend :11: failry quickly while still kicking towards the surface? Sort of like I was being pulled back down. No problem, I just added a quick shot of air in BC to get bouyant stopped a minute or two to check everything. Then continued my ascent just as I had been no other problem to the surface. Did I in advertantly let out too much air from BC on way up? :06: This was my first dive at this depth.

 

[pants!]

Vented too much air.

 

[cummings66]

gentle slow ascent holding up BC valve to let out air is it expanded. All of a sudden about 20 ft (not sure last check on guage was at 30 ft and several more kicks later) I started to descend :11: failry quickly while still kicking

It sounds to me like you were overweighted if you dropped that fast. At 20 feet you shouldn't really have much air at all in the BC which is why I kind of think you were too heavy. Even if you vented all the air out at 20 feet you shouldn't drop as fast as I think you're saying you were. That's one of those hard things to judge without seeing you actually drop. How did you check your neutral bouyancy?

50 feet doesn't figure that much into it as long as you keep up on the release of air, but I suspect you did let out too much since in a quarry there really is no current to mess with you. The real question is how much air did you need in the BC to remain neutral at 20 feet?

 

[1RUSTYRIG]

Did you have a lot of water in you BC bladder after the dive? I have seen divers continue to vent their BCS when there isn't anymore air in it and have it take on water....

 

[PADI Knight]

It sounds to me like you were overweighted if you dropped that fast. At 20 feet you shouldn't really have much air at all in the BC which is why I kind of think you were too heavy. Even if you vented all the air out at 20 feet you shouldn't drop as fast as I think you're saying you were. That's one of those hard things to judge without seeing you actually drop. How did you check your neutral bouyancy?

At 20 feet you shouldn't really have much air at all in the BC. That's what I thought when it happened.

The real question is how much air did you need in the BC to remain neutral at 20 feet. Very little just a 1-2 second burst of the inflator. Like when doing a fin pivot.

Bouyancy check prior to dive on surface weight 198 myself had 13 lbs mask half under water with empty BC holding 1 breath. Ascent to 50 ft was fine no problem with bouyancy or descend rate while down didn't even touch the boat woooooo hoooo. I figured I just let out too much air from the BC but don't remember a discussion of this happening during OW class though.

 

[PADI Knight]

Did you have a lot of water in you BC bladder after the dive? I have seen divers continue to vent their BCS when there isn't anymore air in it and have it take on water....

Ahh come to think of it yes there was quite a bit more than during certification dives now that you mention it.

 

[1RUSTYRIG]

Ahh come to think of it yes there was quite a bit more than during certification dives now that you mention it.

Water doesn't float

I have been diving quite a bit longer than my wife and saw her do that a number of times after cert. Don't feel bad, everyone has done it a time or two.

If you find yourself have problems staying down for a safety stop it is also a good way to add the few pounds you forgot on the boat

 

[PADI Knight]

Water doesn't float

Yeah it was a good learning experience for sure.

If you find yourself have problems staying down for a safety stop it is also a good way to add the few pounds you forgot on the boat. Actually once I shot a puff of air in the BC I settled down was bouyant while I checked everything out then headed on up. Really freaked my daughter (my buddy) out though when I got to the surface just after her. She didn't see me signal something wrong and thought I was heading back down till I stopped. Gave us a good chance to work on communication signal before we go to Myrtle and reef dive.

 

[gregor1234]

Water doesn't float but it doesn't sink either.

If you have a little air in your BC and you let some water into in to BC (even a lot of water) without letting any air out, you bouyancy should be unaffected. The additional volume of the water will add to your drag and the additional mass will add to your momentum, but its weight will be exactly counterbalanced by the bouyant force of the water surrounding it because the water you let into the BC is the same identical water that is around you that is bouying you and your BB bladder up

I agree it is easy to get water in the BC and I do it all the time by wrongly opening the shoulder valve when I am in a fins-up attitude. I doesn't affect my bouyancy however (except that opening the wrong valve fails to have the desired effect).

The introduction of water in the BC can only effect maximum bladder bouyancy (when completely filled with air) where the added water then excludes some of the bladder volume that should be occupied by air. This would be a problem only when trying to get the full 45 lbs of bouyancy out of your BC and not when nearly neutral during an ascent.

I would agree with cummings that you were slightly overweighted, then vented a little too much. And I would be willing to guesss that you a) had air trapped in you wetsuit and b) were holding a very big breath when you did your initial bouyancy check at the dock and were over weighted as a result of those two factors.

 

[CIBDiving]

Water doesn't float

It doesn't Sink either - it makes No difference how much water is in his bc!