It's also pretty rare to step on the deck of a sub when it's out at sea. Unless you're doing something like launching/recovering a boat or the like. It would be useful to know what he was supposedly doing. Or did he mean he was up on the sail and the story just got the terminology wrong? Something else to contemplate.
Stingers and maybe a little gismo launched out or the "tubes" the kinda floats on the surface bobbing nose up when the anti sub plane or whatever flies over....well surprise....just guessing don't know for sure.