The real challenge here is avoiding the constant bombardment from the barge. After your 300th attempt, though, dispatching these foes will barely be an inconvenience.
The barge stops occasionally to drop off enemies to fight which can be challenging on their own. While there is no way to target the barge directly, that won't stop the thing from harassing you for the entire fight.
It is the hardest thing you'll do in the game, so that's good enough for us. This encounter's status as a 'boss fight' will probably be disputed by some, but it features a recognizable primary threat The Barg.
