There was a community project done on the unity forums but it will require a great deal of polishing to make it work.
I made a post over there about the subject not too long ago maybe you can find it in my recent posts. I think the thread was titled "Look at this water" or something.
Unity doesn't have any quality water system. A few people have done projects unrelated to unity and have been asked to port them over since there isn't a good system available but unfortunately while there is potential for someone to do it the actual product does not exist yet. At this point your best bet would be to manually noise animate a plane with a water shader of your choice and find a way to imply motion to the boat, probably manually on a loop.
