H2Andy:
dweeb, you are amazing... you manage to find a thread wihtout a single troll in it
after 53 posts, and then you post not one, but THREE trolls back to back to back
The only troll is the first post in the thread.
You asked something that is covered in PADI OW Module 1!
You're a well-educated professional, and supposedly a certified diver. I'm sorry if it hurts your feelings, but if you REALLY didn't know what you were asking, then you should return ALL your C-cards to the issuing agencies with a request they be revoked. This is so fundamental and basic. It's the entire foundation for buoyancy control.
My initial response was sincere - is this a joke?
When I first read the question, I was annoyed. When I saw your name on it, I was aghast. While I may often disagree with you, I believe you're WAY too smart for that question.
As a lawyer, how would you respond to another lawyer who asked "What's the Fifth Amendment?" Hopefully, the same way I'd respond to another software engineer who asked "What's a byte?" Your question is the equivalent for a diver. It's like a blimp pilot asking why they don't use bags of air to anchor the blimp.
That you do not grasp this basic diving concept is evidence that your OW instructor pretty much violated the standards of every agency in certifying you. There's a question in PADI Module one that can't be answered without knowing what you claim not to know, and there's a place for you to sign and acknowledge that you have had your answers reviewed and your mistakes adequately explained. Your question means either you signed a lie, your instructor certified you knowing you hadn't met the standards, or that your retention abilities approximate those of a sieve. I choose, based on your education and profession, NOT to accept the last of those three, and accord you the assumption of personal integrity to discount the first as unlikely, so clearly, there must be a problem with your instructor.