Koopa Troopa Sub
In the boss battle, a submarine shaped like a mechanical Super Mario Bros. styled Koopa Troopa will arise from the dull waves of the sea. It has a somewhat of a dark blue cockpit with a Koopa Troopa piloting it. In between the cockpit and the mechanical Koopa Troopa body is a gray layer of three cannons. One is right beneath the cockpit, and the other two are on each of the sides of the submarine. At the start of the fight, the Koopa Troopa will have his cockpit open, exposing himself and allowing Mario to get the first few hits. Sometimes, he will turn sideways to prevent himself from getting shot by Mario, as the sides of the submarine are closed at all times. The Koopa Troopa's attack method is firing out of the three gray cannons that are in the middle of the submarine. He usually fires out of the cannon in the front, because he is facing forward for most of the fight. If he is facing sideways, he will fire out of the cannons that are on the sides of the submarine. His projectiles are small, light green balls that are pretty easy to avoid, as their fire speed is a bit slower than other bosses. Frequently, the Koopa will dip his submarine into the water to temporarily avoid Mario's attacks. The further Mario and Yoshi get into the fight, the submarine will start to move to the sides faster, as well as turning the other direction as his defensive move. He also appears to dip his submarine into the water faster, too.
Once Mario has dealt enough damage, the Koopa will get angry and dip into the water. Once he comes back up, all three cannons will now be facing forward, and the cockpit is entirely guarded. The mechanical Koopa Troopa's face is now smiling with its mouth open, as to before he was smiling with his mouth closed. The new enhanced Koopa Troopa Sub is even faster than before, the firing speed is quicker, all three cannons sometimes fire all at once, his turning speed is faster, and his agility is faster than before. In order for Mario to defeat the new submarine, he must shoot the smiling mechanical Koopa Troopa face at the bottom of the sub, while avoiding his triple cannons.