We're not knuckleheads. Any functioning adult is well aware that movie violence isn't any more realistic than movie sex, drug use, police procedure, or dinosaur DNA accessibility. No one picks up a gun and expects it to have an endless supply of screaming Rambo bullets, the same way no one thinks movie guns show anything resembling the real trauma they cause. Unless, of course, it's something like Saving Private Ryan, which portrayed D-Day as Hell's wailing beach party.
More people probably died making this scene than in the real D-Day.
Only here's the thing: That shot of WWII bullets whizzing dangerously through ocean water is a terrifying lie, because every real-world test of this scenario results in the bullets breaking apart or slowing down just a few feet after hitting water.
Much like the male anatomy, guns seriously under-perform while underwater.