Much depends on the prevailing winds. Onshore or offshore. If onshore how high are those winds & how much salty mist is in the air. I live less than 1000' from the ocean. I can always hear it. Salt spray is not too much of an issue except on stormy days. Unpainted things rust quick around here. What does not rust corrodes.
RVs are put together with cheap fasteners. Frames have a very thin coat of paint. If you are going to spend any time near salt water rinse frequently especially undersides & moving parts for the slides.