Clipper class ship.
The Arcanium Steamboat is a Clipper Class boat that can be purchased from Steam. This boat is included when purchasing the Arcanium Expedition Pack from the Steam Store. This item is one of the many Store exclusive Items that can be a rare drop from Chaos Chests.
Like all other Clipper class ships, it houses a cannon which when the attack button is held, the cannon will aim towards the mouse. Releasing will fire the cannon.