You know for being infinite the Outer planes don't have much in the ways of Oceans. Though think of it there is no reason for them not having oceans. Perhaps an oceanic part of the gray waste, a seemingly endless sea dotted with dreary islands and ever raging storms where titanic fiendish navies face off?
The only naval feature mentioned running through the lower planes is the River Stix, but perhaps could one take a cue from Norse and other Mythologies and connect the outer planes with a vast ocean with currents that slide between the planes? Some planes it doesn't work for, Carceri comes to mind, though you could have a large waterlogged cube, but others it could work very well.
What oceans and seas are on the outer planes? I can think of the Styx and the ocean around Mt Celestia. Might be an interesting game, great Devil and Archon Navies lined up on a vast ocean under the gears of mechanis, neither side moving much as both are playing by law and have reached what seems to be an eternal stalemate on the plane of law.