As part of a Sea Scout Ship, how involved was this boy in the trip planning? The requirement says, "On any of these camping experiences ... Plan and carry out a float trip...". If he was along for the ride, but didn't do the planning, then it won't count and you don't have to worry about it.
As for 'camping' on the ship, I would likely count it if he slept on deck. Sleeping in the cabin is surely not "under the sky or in a tent".
Eagle Scout 1987
OA Vigil Honor 1986
Fox - WE7-590-05-2
Currently - Troop/Team/Crew Advancement Chair & Dist Webmaster
Previously - SM, MC, CM, ACM, ADL, ASM, COR, Dist Camp Chair, PL, SPL, Scribe, Songleader, JASM, OA Chapter Officer, ...