Indeed Will...
But then I see no reference to them being dropped from a hot-air balloon. They were dropped from a bomber, perhaps a V-bomber's bomb-bay, travelling at that sort of speed - though there is no specific information to that effect other than it was a 'high-flying' bomber - 30,00 ft is too high for a piston engined bomber, so humour me and assume it was a V-bomber and at speed not about to stall...
They did however seem to be pretty sure that 'lapping' waves can 'surprisingly' undress someone in a couple of days, as they weren't denuded after a fall.
So if it really matters, we can conclude that we can't conclude what did it - if the reports are correct, which I imagine they basically are.
PS. I was just simply adding some (rarely) known facts to a previous question about their reported clothing states