Boats are items purchased in Ninja Fishing in the shop. They spawn different treasure items when on different boats. It's unpredictable to tell which chest will produce an item.

Here are all the boats so far:

Boat Cost
Dinky Fishing Boat 0 coins (Default)
Rubber Ducky 2,000 coins
Viking Ship 20,000 coins
Steamboat 50,000 coins
Flaming Pumpkin Boat 65,000 coins
Xmas Boat 75,000 coins
Time Machine 90,000 coins
Twitter Boat 0 Coins (Promotional)*
Arcade Boat** 0 Coins

*Log in with Twitter and post the message given

**Limited Time Only