Water is hard on airplanes, and salt water is brutal. Long-term seaplane ownership and safe operation depend on diligent corrosion control.
Salt water accelerates electrolytic corrosion of aluminum and steel, attacks electrical connectors, and leaves a conductive, hygroscopic residue that keeps corroding long after the airplane is out of the water. Operating in salt or brackish water demands a maintenance discipline that fresh-water operators can sometimes relax.
After every salt-water flight, rinse the entire airframe with fresh water — floats, struts, control surfaces, landing gear (on amphibians), the engine and prop, and especially crevices and the float interiors. Many operators flush float compartments and run fresh water through to displace salt. Lubricate cables, hinges, and fittings on a tighter schedule.
Beyond corrosion, protect the airplane from impact and grounding damage: keep the prop out of spray as much as power and technique allow, avoid running floats onto rocks or unknown bottoms, and watch for floating debris, deadheads (waterlogged logs), and shallow obstructions. A small dent in a float bottom can disturb the planing surface and add drag or cause spray to strike the prop.