In most cases there's a head up to top brass though so nobody gets hurt in the process.
When I was stationed in Germany we were constantly getting probed by friendly SpecOp d00ds during alerts. They'd walk around our motor pool putting stickers on vehicles and grabbing equipment that they'd later hand over to the very unhappy full-bird.
He'd in turn have us join him in his unhappyness by calling 4 wee-hour alerts in the next week until we got it right.
It kinda sucked but it was good training.
When (authorized) divers are in the water working all know it to include those standing watch. Not sure of the current threat con but I'd rather stand captains mast for shooting a carp or even a PADI/NAUI sport diver than letting someone blow a hole in the hull with a soviet SPM limpet mine.
Too many multi-lingual postings and surface patrols and troops standing watch for someone to accidentally swim a few miles or so to peek at a big ole boat.