G.U.N.B.O.A.T.

The Big Unambiguous Boat of Aiming at Towers is a semi-blimp that only appears on tracks with water on them. It first appears at round 20 and appears at random rounds afterwards. It doesn't use the track, but scoots across the water area and then leaves the map if it's not disabled. You don't lose lives if a G.U.N.B.O.A.T. escapes. It's impervious to damage. However, you can disable it by buying a monkey tower, placing it on the G.U.N.B.O.A.T., and upgrading it 2-2. When it's disabled, the G.U.N.B.O.A.T. is replaced by a 0-0 Monkey Buccaneer. You can upgrade this.

Abilities

 * Barrage: Fires bullets at random towers across the map. Each bullet deals 8 HP damage, and explodes, dealing splash damage to all towers within the radius of a 0-0 Bomb Tower bomb explosion.
 * Grapeshot: Fires a single bullet that shatters into five small bullets that deal 3 HP damage each, but they scatter over an area the size of a 2-3 Monkey Buccaneer's search radius.

Trivia

 * This is an obvious expy of the Gunboat mooks that were recently added to Kingdom Rush: Frontiers.