The trick to not having your boat stay put is:

A. Having nobody ON the boat, otherwise, yes, it will still do what you last had it do.
B. Parking your boat away from the ocean. By that, I mean a large enough distance from the actual ocean biome. It does not need to be the up a river, but just far enough into the shallows. You will always find a nice little bay of some sort. There will be no waves to throw it around. Job done.
Take this into consideration when building a dock or boathouse. It would make your life much easier.