Marine Foam ??

[msbhammer]

The big late night question here that is spinning around in my head. While do my rewiring job and running some wire down along the gunnels, I noticed that I was able to stick my fingers down between the the gunnel and floors in a few spots. I wanted to shoot in some spray foam to fill any gaps that I dont see under the floor and maybe run some along the floor line of teh gunnels for extra buoyance. Is there a speacial type of foam I can by in a spray can with the old plastic tube, you know, like liqued nails you use in a house ???
Seens pics of guys installing new fuel tanks, what did ya all use ??
Is liquid nails suitable or will water absob into it and make it heavy. Trying to stay away from the two part stuff.
Thanks,
Mike.