Sea spray? The 1V may be the best weather sealed of the 3 but don't take any camera into sea spray! Salt water ruins everything electronic. I'd take an old manual camera and lens, something cheap and replaceable like manual focus FD gear, a TX or FTb that only uses battery for meter. That way there is little to be ruined by salt water and if it is ruined it is easily re-bought.
Also remember that you must use a sealed L lens (usually with front filter) to finish the sealing. Otherwise, water can in through the lens and its mount. The lenses with a rubber seal at the mount are sealed (also sealed under all focus/zoom rings and switches).
Of the three, I have an EOS 1N RS but as I said I take my old FD gear for sea shores.