Is it possible to train yourself to see clearly underwater?

No: Water bends light differently than air. This is why a stick appears bent when it is held partly above water and partly submerged. Our eyes are built to see in air and cannot adjust for the different light bending that occurs in water. Similarly, fish can see very well in water but would be blurred trying to see out of the water. Goggles create an air space for our eyes to see when under water.

Not really.: You could try squinting for added benefit.