A few years ago I rode the pirate ship with my language school class. The pirate ship seems a bit odd in a tranquil place like this, but it still was cool experience and got some interesting pictures with the boat out of it. The only point was that it was a very windy ride if you're out on the deck, but that can simply be helped by going inside the ship. Last month I visited lake Ashi again and me and my boyfriend rented a small rowing boat from the locals. I think it costed about 700 yen for one hour, this was definitely a more private, quieter, less windy boat ride which I absolutely loved! I definitely recommend to rent a small boat yourself