The term 'Hydroplane Part' is referring to a FLOAT, which is a buoyant device that is used to keep a boat or other watercraft afloat. Floats are typically made of foam or plastic and are attached to the bottom of the vessel. They help to keep the vessel stable and prevent it from tipping over in rough waters. Floats also provide additional buoyancy, allowing the vessel to remain afloat even when it is carrying a heavy load.