It's time... For SCIENCE!
Or possibly dorks talking about super hero powers.
This one time, at Mythbusters camp, they were testing whether you could bulletproof a car with phone books, and they kept escalating the firepower, and it's like, no, nothing is bulletproof, except maybe deep water, and you have to establish a range in which the myth can be confirmed, because otherwise you'll inevitably get to a big enough gun, and then "busted" becomes the default outcome, AND I LEARNED THAT FROM WATCHING YOU, MYTHBUSTERS, I LEARNED THAT FROM WATCHING YOU
(Turns out water doesn't compress and will totally mess up bullets, so it's for all intents and purposes bulletproof past a few feet, but even then you could probably build some sort of bullet projection device that could get through a given body of water, though that would potentially require a system so unwieldy as to be impossible to construct with earthly materials within atmosphere, and might require extraterrestrial assistance in order to be constructed.)
(That's just layperson speculation, though. I am not an engineer or an extraterrestrial.)