Water will stop bullets. Complaining about waves stopping bullets is just as aimless. Additionally, the 5.56 Nato round in not rated to travel 30-40 meters underwater and neither is any other standard rifle cartridge. Even if some rounds manage to penetrate the surface of the water, we are unlikely to see any severe damage from that bullet as it'll be dropped to less than acceptable velocities almost instantly. Doesn't mean you can't shoot for the mouth when they pop out ;) I think this has been discussed enough.