re-enforced vinyl. This stuff is used in commercial applications all over the world. The seams are connected with the same stuff SEAWORLD uses to create their custome made floats.
If by chance you took a razor to the bladder, it would be patchable, easily patchable. Trying to cut this stuff is not very easy. You need high end shears to cut it.
This pic is of a prototype and is not what kayatank is selling. I was one a the luckily to test this puppy.
