This “looks” like it’d do the job. Now if it would be long enough...
You just need to get up off the deck a few inches so the water can run
under the tent. Some kind of pallet sort of thing a little smaller
than the tent should work. Then the water would run off and under the
floor of the tent. A nice Marriott is better tho ;-)
Small tent with an air mattress would be better.
I suppose if the air mattress is under the tent.
I was really thinking about something where the water could flow tho.
I guess I am thinking about tropical rain where you can get an inch or
more in 15-20 minutes.
The bottoms of decent tents are waterproof. The rain just goes under or around. It's not as though
he's going to have five inches of rain accumulating on the deck of the 'tooner. Something like this
would fit the bill easily: