The Sunk Boat is an unimplimented/planned feature found in the game files. Currently, it can only be spawned in with the Lua Console, using the code DebugSpawn("sunkboat"). However, it will not have a texture, though it will block the player. The image is taken from the game files. Originally, it may have been how the player arrived on the island, as when Wilson examines its counterpart, the boat, he says, "Is that how I got here?"