Floatation under the floor is a desirable trait for any small boat,
especially in a dinghy. with it, the floor should be self bailing;
that is, when empty with a drain plug out, the boat will drain itself
dry. with a plug in, it will not take in water when loaded. This
suggests a double hull, or alternatively floats under the seats, not
nearly so good an idea, as they will not allow self bailing.

I have often thought I would like to make a boat out of polyurethane
foam like pool planks, clad in sailcloth and velcro so as to lie flat
as cockpit cushions or form a wet, floppy, unsinkable floating toy
bathtub of a boat. Dogs and kids might love it.

Make it with waterproof material and a spine, it might do even better.

The thing about stitch and tape is that the wire ties are actually
alignment guides. Spanish windlass, clamps, glass tape and resin do
the hard work.

Terry K