Salt air is harder on a chain here than mileage is anywhere else, and a chain is the cheapest part on a bike to look after and one of the dearest to replace along with the sprockets.
Properly means degreaser on, a brush on all four faces rather than just the top, a rinse, a dry, and lubricant put on while the chain is warm from being turned so it works into the rollers instead of sitting on the plates.
What it is not is a can of spray over the old grease, which is what most bikes arrive wearing. That builds a black paste that holds grit against the rollers and does more harm than nothing at all.