Let's talk about the most common method of doing a weight check. You get in water too deep to stand, dump all the air out of your BCD, and hold a normal (not big) breath. You should float at eye level. If you exhale, you should sink. With that in mind, a recreational, single tank diver should have no trouble staying at the surface without air in the BCD, unless that diver is significantly overweighted.
Now, if you are diving something like a two piece 7mm suit and lose all the air in the BCD at depth, you may find it hard to swim up to the surface because of suit compression. If so, you will need to dump some lead. If you have all your weight on a weight belt, that is not the best situation, but you will certainly get to the surface. That is one of the advantages of weight pockets--dropping just one of them should do the job.
If you cannot dump weight, you are getting into the same issue technical divers have. They often have to dive so much overweighted that they could not possibly swim to the surface in case of a wing failure, and they have no weight to dump. In that case, they will use redundant buoyancy. The most common form of that is a dry suit. Another way to do it is with a dual bladder wing.
Now, if you are diving something like a two piece 7mm suit and lose all the air in the BCD at depth, you may find it hard to swim up to the surface because of suit compression. If so, you will need to dump some lead. If you have all your weight on a weight belt, that is not the best situation, but you will certainly get to the surface. That is one of the advantages of weight pockets--dropping just one of them should do the job.
If you cannot dump weight, you are getting into the same issue technical divers have. They often have to dive so much overweighted that they could not possibly swim to the surface in case of a wing failure, and they have no weight to dump. In that case, they will use redundant buoyancy. The most common form of that is a dry suit. Another way to do it is with a dual bladder wing.
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