I remember when I first did Dragon Slayer quest in RSC, I was so excited when I got Lady Lumbridge the ship, thinking I would be able to sail the seas.  I think it would be cool if you implemented a sailing skill or just allowed ships, perhaps making pirate pk battles or islands (idk).  Maybe tailor it in to the potential Clue Scroll idea?

Just always wanting a ship I could ride in RSC besides the trawler and short trip to Crandor