This is one of the very few times I agree that a filter would be useful--if you are at the ocean exposed to blowing spray and whatnot. Buy a quality multicoated filter and always use the lens hood.
A ND or CP filter can also be useful in certain rare circumstances, but if you need to ask what they do, you probably don't need them. Totally different animals. Again, buy quality.
okay, then probably I'll just have a good quality filter and not the ND nor CP as I really don't know yet how to use them, i'll have to out-grow my body and lens at the moment (10-22, 50 1.4, 18-55 IS II, 100MacroL) and better save the money for my planned 70-300L or 35 F2 IS or Ziggy 35 1.4