If one is going to toveil keilim in the ocean, does it have to be done in a place where the water has not passed over or around a manmade structure, such as a breakwater or pilings or the supports of a pier? For example, at the separate beach on the Tel Aviv shore, out past the end of the swimming area, there is a breakwater. Would it be okay to wade in a little way from the beach and toveil keilim there? (In other words, does the problem that applies to rivers also apply to the ocean?)

Yes, it's easy and kosher to tovel in the ocean.