Will salt water harm the Purple® Seat Cushion? Great question! Our Purple® Seat Cushions will not be harmed by fresh or salt water. Related articles Can I cut the Purple™ Seat Cushion to fit a specific seat size? Can the Purple® Seat Cushions be used in the shower? Can I cut the Purple® Seat Cushion to fit my motorcycle seat? How do I clean the Purple® Seat Cushion? How do I take care of my TempBalance Duvet?