Does the foam absorb water?
No. However, water can work its way through the foam under pressure or by gravity force. When the foam is placed on water it will float and upon removal it will not contain any water and it does not lose any of its insulating properties. But, if it is immersed under water, water can be forced into the foam by the hydrostatic pressure; however, once it is removed from water and allowed to dry out, the original insulating properties will return.