Brit sump divers make use of their dry suits for bouyancy, but then their dives are typically short and shallow (a tool to get to more remote sections of a cave, so gear is scrutinized for transport between sumps.) If you are doing longer dives to deeper depths you can see sme fairly major weight swings as you consume the gas tht you are carrying. This is exactly why early divers started carrying gas cans and clorox bottles with them until someone finally invented the BC.