It sounds to me like a US Navy Mae West would fit the bill very well for body surfing. There is a spot to clip on the single "D" cell strobe light, a place to tie off a signal whistle and signal mirror.

I used to wear one (a Mae West) on Flight Ops in the WW2 style (deployed & deflated) and I always found a little extra room in the storage bag for a few granola bars.

Using what is available today in the way of water pouches and other appropriate survival equipment tidbits, I think it would fit the bill very nicely. The Mae West has a co2 cartridge and a separate tube for manually inflating.