I would imagine that they are smart enough to not pull pranks that are actually dangerous. Part of the purpose of the pranks is to find out how the new guy is going to react, on the viewpoint that the time to discover that a guy is a jerk, an ass, or a hysteric is BEFORE the stuff hits the fan.
There are real limits to pranks at sea, so they are generally done on land, if at all, and since these sailors are looked after like family, the pranks are not ones to cause harm to the other crewmembers in any way- all their lives depend upon it. Again, this is not like a surface vessel, where people get away with a lot more. I might add a caveat.. about which see the USS Iowa and the so called “investigation”.