The Tug Boat is a very large and very slow boat in GTA IV. It can usually be found near the barges in the Humboldt River between the Broker and Algonquin bridges. It can also be found in the dock in the south east of Alderney. It is the largest boat in the game, and probably the entire series yet.
Whilst on the Tug Boat, your character cannot run. However pressing the correct button to board the ship will also cause your character to automatically walk to the wheel of the boat wherever you are on the boat. As this vehicle can only properly contain one person in multiplayer (the driver), others can still stand on the deck, however all other characters will lose some control of their characters making it really hard for them to move.
NOTE: When on the Tug Boat, if you aim with the pistol (hold L) you can walk faster.
When the boat is moving, any other character on the boat will also begin to glide off slowly, and if you are stood at the front of the boat you can actually pass through the built up area of the boat and see the water beneath it.
When, and if you can get this boat to explode, it will keel over just like the wrekage you will see on the coasts of Alderney.
When in the water, you can board the ship by pressing jump and the character will do a giant leap for the side (glitch).
Also, thanks to how incredibly top-heavy this boat is, a good whack to the top part of the boat on either the left or right with a helicopter will make it capsize. This has happened before.