How did that happen? Our MarDet would occasionally do live-fire training off the flight deck (CVN-65); they naturally pointed their weapons away from the ship ....
Or are you talking about hitting the hull of a different ship, e.g., one of the tin cans in plane guard, or alongside during an UNREP? Seems like that would ... get noticed by a lot of folks.
Also note how wide an angle "ship hull" represents both vertically and horizontally.
Not so 1 in a million.
But what's the chance of a bullet that hits water bouncing back the other way at high speed? I would have thought it was zero!
Sure. That's why these safety officers exist. I think some other funranium posts state.that (paraphrased) "safety rules are written in blood."
That said, I suspect folks like that would tend to phrase the rule in a way to diminish the implied impact/likelihood, rather than enhance it or state as-is, as (afaict) the original did.
What could possibly go wrong?