i am looking for a product that resembles Great Stuff insulation foam yet that does not absorb water once it dries and forms its final shape.

i decided i would ask here, even though it is not for home improvement reasons that i am looking, because i figure you guy would have a comprehensive grasp on all sorts of building materials.

here is why i am asking: i am trying to build a poured, anatomically shaped foot bulkhead for my whitewater kayak. the space is very tight and inaccessible so the best way to shape it is to sit in, put something over your feet and inside the boat to protect from stickiness, spray the foam and wait for it to dry.

the problem with Great Stuff is that it is permeable and swells once it absorbs water. so i am looking for something like it that is water impermeable yet can be sprayed into a shape.

thanks,

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