Buddies kept grabbing/pulling me to ascend faster than computer said was safe

[Pinecube]

You should always try to be always neutral in the water, except for when you want to ascend, then you should be negative. ...What?

Unfortunately, this instruction is indeed given to many divers. When I was a new DM, I heard a Course Director tell new OW students to do that. When I was leading a group trip to Belize, a veteran DM gave those instructions to our group before our first dive together. I assume that advice was part of his regular dive briefing to all groups all year long, year after year after year.

What do the two have in common? Neither had any experience other than warm water diving in 3mm wet suits, hopefully close to properly weighted. That system will actually work under those circumstances.

Thanks for the explanation. I've been trying to wrap my head around why you would release air in order to asend. I guess it's a less critical in warm waters.

 

[boulderjohn]

You should always try to be always neutral in the water, except for when you want to ascend, then you should be negative. ...What?



Thanks for the explanation. I've been trying to wrap my head around why you would release air in order to asend. I guess it's a less critical in warm waters.

If you are properly weighted in a 3mm suit in warm water, your BCD should be nearly empty at the end of the dive, so dumping the air in it won't make a lot of difference. If that's all you know, the advice to dump all the air makes sense. Diving under other circumstances is a different story.

 

[doctormike]

The instructor who told you to dump all your air before ascending should be shot at the post.

A lot of people have jumped on this bit of advice, but there is something to it, in the proper context.

If you are correctly weighted, your wing shouldn't have a lot of gas in it as you start your ascent. Now if you are (a) significantly overweighted, and (b) on a wall dive, it is true, emptying your wing a recipe for disaster. But you shouldn't be significantly overweighted, and having a lot of gas in your wing as you start an ascent may set an inexperienced diver up for a runaway ascent.

The gas in the BC during a dive is there to compensate for the two things that change buoyancy during a dive - exposure suit compression at depth and the weight of the gas that is consumed during the dive. When you start your ascent, it ideally should have just enough gas to compensate for suit compression, which might be minimal with a thin wetsuit in the tropics.

Most of us are probably used to just dumping gas as needed on ascent. But assuming that you are not overweighted, you should be able to swim off the bottom with an empty BC, and if you can do that, you have removed a potential cause of a runaway ascent.

 

[boulderjohn]

If you are correctly weighted, your wing shouldn't have a lot of gas in it as you start your ascent. ... But assuming that you are not overweighted, you should be able to swim off the bottom with an empty BC, and if you can do that, you have removed a potential cause of a runaway ascent.

Here is what the OP wrote:

We started to ascend and at first I was having trouble going up because I had emptied all my air .

Do we assume overweighting?

 

[doctormike]

Here is what the OP wrote:
Do we assume overweighting?

No, we didn't, for the OP. But like most discussions, these comments are read by new divers trying to learn about diving in general.

I just thought that I should provide some context and nuance to the idea that an instructor who recommends dumping air before ascent is an idiot who should be shot, which seemed to be the implication of a number of other posts.

I actually thought that you were doing the same thing!

Also, the OP said "AT FIRST I was having trouble going up". Which implies that she was able to ascent more easily as her suit (and possibly the gas left in her wing) expanded. Not the worst thing in the world to have to kick a bit from depth, especially if a hard bottom and properly weighted.

 

[boulderjohn]

Also, the OP said "AT FIRST I was having trouble going up". Which implies that she was able to ascent more easily as her suit (and possibly the gas left in her wing) expanded. Not the worst thing in the world to have to kick a bit from depth, especially if a hard bottom and properly weighted.

We don't have to guess why she had trouble gong up. She said explained it:

...because I had emptied all my air

 

[Crowley]

I think we need to clear a few things up here:

- Regardless of whether a diver is correctly weighted or not, dumping the air from a BCD prior to ascent is not, and never will be, correct ascent technique.
- A correctly weighted diver in a thick exposure suit is, at depth, going to be negatively buoyant.
- For a correctly weighted diver, the amount of air in a BCD at depth should make it look and feel as if it's almost empty - one of the classic signs of an overweighted diver is somebody down at 30 metres who has a fully inflated BCD - but that's still a lot of air
- The fact that the OP dumped air prior to ascent and was slow to swim upwards does not necessarily mean that they were incorrectly weighted, however it is also fair to say than many inexperienced divers are, indeed, overweighted either by themselves or by their DMs and instructors.

Without having been there, and with all due respect to the OP - we may never know. There are many possible factors at play here. I do not believe that instructors who teach students to dump all their air prior to ascent should be shot - but they do need to back and read some very remedial material concerning correct buoyancy control.

And more to the point - and the topic of the post - the 'advanced' divers who manhandled the OP should have approached the situation differently.

C.

 

[dmaziuk]

Do we assume overweighting?

Mmm... I tend to dump all air at the surface and start feeling heavy at around 25 m down (tropical seawater). If it's your first time at 30 and you don't know yet that you'll be a bit heavy down there, that may be why ("at first"). Now the OP knows, and also knows that dumping all air at 30 m is not the wisest move.

 

[victorzamora]

No, we didn't, for the OP. But like most discussions, these comments are read by new divers trying to learn about diving in general.

I just thought that I should provide some context and nuance to the idea that an instructor who recommends dumping air before ascent is an idiot who should be shot, which seemed to be the implication of a number of other posts.

I actually thought that you were doing the same thing!

Also, the OP said "AT FIRST I was having trouble going up". Which implies that she was able to ascent more easily as her suit (and possibly the gas left in her wing) expanded. Not the worst thing in the world to have to kick a bit from depth, especially if a hard bottom and properly weighted.

Why would you want to have to kick upwards? Instead of dumping all of my air and kicking vertically to ascend, I simply breathe in. This starts my ascent, which expands the air in my BC and increases the buoyancy of my suit. As I start rising steadily, I dump some gas to slow to almost a stop. Another big breath, and I do it all over again. Eventually I get to the surface, easily matches any ascent rate you could want, and I do it with litterally no more effort than pulling on an OPV string. Why would I EVER kick to go up?

 

[doctormike]

Why would you want to have to kick upwards? Instead of dumping all of my air and kicking vertically to ascend, I simply breathe in. This starts my ascent, which expands the air in my BC and increases the buoyancy of my suit. As I start rising steadily, I dump some gas to slow to almost a stop. Another big breath, and I do it all over again. Eventually I get to the surface, easily matches any ascent rate you could want, and I do it with litterally no more effort than pulling on an OPV string. Why would I EVER kick to go up?

I tried to add a little nuance to the discussion, since some new divers don't understand what the BC is really compensating for, and what the logic might have been behind advice to dump some air before an ascent. I didn't mean to recommend kicking off the bottom as the standard technique for initiating an ascent.

I apologize if I was unclear.