You do not want to gather water from the ocean.
Shorelines are natures protein skimmer. All kinds of nasty junk gathers there, to include man made chemicals and toxins that will be havoc in our closed systems.
The only way Iíd suggest collecting would be if you could go far out into the ocean. Even then Iíd want to run it through some sort of filter...uv
at the least. Thatís how the big box stores do it when they sell it to you.