Will hypoxic sets improve my ability to swim without air?

From what I understand, breath control training largely provides little (if any?) physiological training effect other than from the work itself (which is hindered anyway, making it a waste of time for training any of the energy systems). I assume there is room to mentally adapt and learn how to manage hypoxic suffering. But other than developing a strong aerobic base and increasing level of conditioning, can one actually have room to improve their hypoxic capacity specifically through hypoxic training? Thank you!