DISCLAIMER: No, this will not suggest massive galleons, frigates, sloops, Etc. So if you're one of those people that posts comments about how suggestions are cliche and such withoutactually reading it, you're just making yourself sound like a moron, so...
The cannon boat is, as it's name suggests, is a boat with a canon. The boat is two blocks long and the player can ride in the back, while the canon takes up the front block. The canon has a texture similar to the dropper, and the boat has the texture similar to a normal boat.
The cannon boat is crafted with two boats, 2 iron blocks and a redstone torch in any shape, and the cannon boat drops itself rather than smash apart if it crashes.
In order to use the canon, the player needs TNT or Fire charges. The player can right click with TNT to fire primed TNT or fire charges to fire ghast fireballs.
The cannon boat does damage to entities it comes into contact with while in full motion, and will not break simply by ramming into blocks.
hmm, I don't know about a "Cannon boat". I like boats and i like cannons, but why should they be bound together? I'd rather have to place cannons on my boat than have them set there automatically. No Support.