The foam has a nice density … 0.24 g/cc so it will float for sure!
I like that it is closed cell and the durometer is high also. There is a good chance that this stuff will handle pretty well to a good depth. Only way to see how much it shrinks is to actually pressure test it.
Send me some, I can crush it
Seriously, if the price is right for you, have them cut you up whatever you want and give it a try. I would make sure that you still got enough rear to drive to the surface just in case but the stuff sounds like it has a lot of promise.