-Good propeties for flotation , waterproofing , sound proofing , thermal insulation.
flotation
Expanding Boat & Dock Foam – Lightweight Flotation &
This expandable foam is recommended for void filling in nonstructural applications. It can be poured underneath decks and inside cavities where a lightweight flotation foam is needed to provide buoyancy.
Boat Insulation & Floatation Urethane Foam (2LB)
EASY TO USE: Liquid urethane pour foam has a simple 1:1 mix ratio, expands rapidly & hardens in place in about 5 min. at 70-80F; to build multiple layers for filling under boat decks, pour expanding foam in separate batches