Which of the following has to swim lifetime, to avoid sinking?

Pristis (Saw fish) belongs to Chondricthyes and lacks air bladder, which regulates buoyancy. So, it has to swim throughout to avoid sinking.Pterophyllum (Angel fish), Betta (Fighting fish) and Exocoetus (Flying fish) belong to Osteicthyes. They possess air bladder. They can stay at a particular depth without much expenditure of energy.