I know a little about buoyancy and displacement , but...What does the foam in a boat do to make the boat float after it has been swamped? And that's the only time it does right ?
A boat will only float at the surface of the water when full of water, At least that's the plan.
Is it that the foam takes up space and not let the water completely fill the boat?
In my mind this is the only expiation like a sealed compartment full of air, kinda.
Other wise foam would only ADD weight to a boat.