Interesting Temporary Buoyancy Issue

[Patrick Star]

At least to me it is...

Hello All,

I did an ocean dive last Saturday with 18 lbs. on my weight belt. I was wearing a 1.5 mil wetsuit, a 2/5 mil hooded vest, and a 5 mil wetsuit over all of it. Warm as toast, by the way, with 50 degree water.

I had enough trouble descending that my dive buddy suggested that I needed a little more weight. However, once I worked at it and was submerged for a while, I found 18 lbs. to actually be a bit too much. When fully exhaling, I could lay on the bottom and stay there while breathing. So I don't want more weight.

What seemed to do the trick was giving up on a vertical descent and just diving down, headfirst, with a few fin kicks. Releasing air from my BC was also easier because I used the release valve at the bottom of the vest since it was then closest to the surface. That method seemed more foolproof than getting the hose extended just right and hoping no air was trapped someplace.

My guess is that I had all kinds of air trapped in my suits which was eventually squeezed out by the pressure. I also assume my breathing got better as I relaxed and that helped too, but I suspect air in the suits was the main culprit.

Is getting down with a few fin kicks and head down frowned upon? Is there a better solution you would recommend, given my situation? I am open to any and all suggestions...except for add more weight.

Thank you all.

 

[CanadaDan]

I’ve done the headfirst descent often. I sometimes find I equalize better that way too (that’s a me thing though). Biggest issue I can immediately think of is descending faster than, and loosing sight of, your buddy.

With that many layers it may help to burp your suit at the surface floating vertically. I’ve had hoods retain air as well.

 

[rick00001967]

i think you are spot on with your analysis.

imho that is a lot of neoprene for 50 degree water but a divers tolerance for the cold will vary widely. up here it is quite normal to wear a full one piece 7mm and a good cold water hood (7mm to 10mm). some even ice dive like this. brrrrr. boots and 3 finger mitts help too though. haha

a dry, wet suit is def more buoyant. i often will jump in and flood the suit to get it wet inside and out. it also helps get rid of any trapped air. i hate it. thats why i usually use a dry suit.

i also agree that once you are down, and begin to relax, you def are less buoyant. sometimes it takes 5 minutes to really get in the zone.

if you have no issues equalizing your ears then i see no problem descending head first. the key is being able to equalize and remain in control of your descent rate at all times. i have been diving with many divers who need to do this at the start of a cold water dive.

obviously if you have a descent line, you could use that to pull yourself down as well, either feet first or head first.

 

[Subcooled]

Is getting down with a few fin kicks and head down frowned upon?

Is that not what all the diving legends (and everybody else) used to do in the days of old?
Loss of buoyancy due to wetsuit compression was manageable.

The BCD only becomes mandatory when bottom times grow and lost gas weight is more than we can compensate for with lungs. And some other advanced stuff. It is nice for surface buoyancy, too. Today many have excessive weights and a buoyancy compensator to compensate for that.

 

[kelemvor]

I think the problem you'll run into if you're slightly positive at the beginning of a dive is that at the end, your tank will have a lot less gas in it. Therefore you will be several pounds more buoyant at the end of the dive. That's going to make ascending slowly and holding a safety or deco stop difficult if not impossible.

I generally descend belly first or sometimes headfirst but not because I'm too buoyant to descend otherwise.

If it was just nerves, and a little trapped air then it's no big deal. How do you know that's the case? If you're wrong, you could be in for a bad day.

The answer, as I understand it is to do a formal weight check in the gear you'll be using. A lot of dive boats I've been on (if you're there for a week or more) will want you to do a weight check before they let you do the first real dive.

 

[Subcooled]

giving up on a vertical descent and just diving down, headfirst

Giving up on a vertical descent...
and then descending vertically???

The rear dump exists for a reason (and you found it).

A few fin kicks will help you to descend and then the suit compresses and eases your way down to target depth. Remember though, that upon ascent, the suit expands and makes you more buoyant. You might be able to compensate for some of that by lungs. Nobody wants to kick down while ascending. I tried that in a kind of an emergency and it kind of sucked.

There is the horizontal descent, too, which is preferred by many drysuit divers.

 

[tursiops]

When fully exhaling, I could lay on the bottom and stay there while breathing. So I don't want more weight.

Not a good test of how much weight you need. It ignores the 5-6 pounds of weight lost as your tank empties.

I suspect air in the suits was the main culprit.

Maybe, but suit compression is also a major cause, with that much neoprene.

Is getting down with a few fin kicks and head down frowned upon?

Is is if you have problems equalizing, or if you are overcoming suit compression that way....you want to be able to hold a safety stop with an uncompressed wetsuit.

if you have no issues equalizing your ears then i see no problem descending head first

The issue might be that holding a safety stop is difficult without contsantly finning down.

Is that not what all the diving legends (and everybody else) used to do in the days of old?

They were not concerned about ascent rates or about suit compression (many wore skin-tight drysuits), and did NOT do safety stops.

A few fin kicks will help you to descend and then the suit compresses and eases your way down to target depth. Remember though, that upon ascent, the suit expands and makes you more buoyant. You might be able to compensate for some of that by lungs. Nobody wants to kick down while ascending. I tried that in a kind of an emergency and it kind of sucked.

And you've lost weight from the air you've used from your cylinder. Double trouble....

 

[Subcooled]

They were not concerned about ascent rates or about suit compression (many wore skin-tight drysuits), and did NOT do safety stops.

This probably depends on how far back in time we look, and where. Some wore thicker suits (depends on area, globally), but you are correct on ascent rates and safety stops. And it's not that long ago that 20m/sec was ok, while max 10m/sec + safety stop is ok today. Divers used to be healthier then, too.

An older diver I know told me how they used to swim before freediving and only then moved to SCUBA diving. CMAS used to be demanding.

All of this does not change the fact however, that for a reasonably skilled diver head first is not much worse than feet first. I can do both styles of descents in addition to a horizontal trim descent in a drysuit, and what is doable in such a balloon is certainly doable in a wetsuit.

Please correct me, if I'm wrong.

 

[kelemvor]

Most photos I've seen of diving legends tend to show a person in a bathing suit, triple tanks, double hose reg, flippers and mask on forehead if not in the water. Excluding photos from ads selling wetsuits, I haven't seen very many vintage photos that include exposure protection. I've seen a few, but not a lot.

I'm a new diver by most people's standards having only been certified 7 years ago. That said, my understanding is that the main reason things aren't done in the way that the legends did it is primarily to improve safety. Maybe I'm wrong.

 

[Subcooled]

And you've lost weight from the air you've used from your cylinder. Double trouble....

Yes, indeed, that is a problem. Better have big lungs to compensate...
Many reasons to wear a BCD.