Petg and abs is the best to print with for saltwater. Abs is very hard to print with as any little cooling will make it warp. Pla can be used but if it's under stress it will break apart. Petg is a little tough to print with but once you get it down you will end up with a strong item. Just make sure you do research on what brands people have used. I used hatchbox for my filament.
If you decide to print with abs make sure you have a printer enclosure as the fumes are not good for you. Petg is what I read a lot use for saltwater printing.