Only flew them Twin Otters on straight floats, but In Salt 100%.
The Amphips may have corrosion problems in the retract mechanism after a few days, especially the electrical connections.
More serious is salt spray getting into the flap/aileron mechanism with severe corrosion to the cast aluminum.
Also salt being blown into the tail plane and empennage where rinse and inspection is hard to do, or not doable expect for major checks.
The Twin Otter I flew on floats in the Caribbean 1984/1985 was converted back to wheels and sold to some Pacific Island operator where it crashed from altitude and killed everybody. Structural or flight control failure was not ruled out,
When I flew it back then I watched the flap brackets get skinnier every month and had bad dreams about the salt being blown into the tail 16 times a day, every day.
(We did 8 round trips between STX and STT every day. 16 landings and 16 take offs every day, flight time only 18 minutes, the Twitter was drenched in salt all day, every day.)
These airplanes was designed for flying on lakes in Canada, no salt, no maintenance..
