Hi- I asked the same question on the Baidarka listserver and was told that the expanding foam will absorb water over time. Maybe the 2 part doesn't? Check out Defender Marine Supplies on the web-I think they stock large blocks of foam. Jack

: What you are asking for may be the 2 parts pour in place urathane foam. Home
: Depot stock those -- usually in the paint section. Just ask for marine
: product or fibreglass area. Good luck.