Children belonging to the Moken tribe in Southeast Asia are trained from a very young age to narrow their pupils when swimming underwater. This lets them see underwater as clearly as we do when we're out of the water. It shouldn't be too hard to create a wraparound facemask that would mimic the effect of narrowed pupils, something along the lines of focusing the incoming light so it would match what was seen when our pupils are shrunk. That way we could all see clearly underwater. If we can't get the optics in the glasses to do the trick then maybe we could find something like cryptochrome that would work on our eyes (this substance forces the pupils in chicken eyes to contract). It could be applied like Visine right before we went diving.