Mega Mech Shark

This unnamed boss, nicknamed "Shark Submarine", is the boss of Wily Castle 2 in Mega Man 9. The Shark Submarine also appears in the Special Stage as a mini-boss.

Strategy
It's divided in three phases: The first part is the tail and releases homing missiles. The second part is the body, which has spikes on it and two hatches that releases small enemies. The last part is its head, which releases several lasers from the mouth.

For the tail, it rises up and down firing homing missiles. Fortunetely, they can be demolished easily by the Mega Buster. When the tail is lower, use the Laser Trident to pierce through the missiles to attack the main gun, which takes damage only when it's opened.

The next part is the chest, which is quite simple if you have any energy for the Tornado Blow. It will blow all the torpedo enemies upwards and damage the hatches. If all the energy has ran out, use the Magma Bazooka to diagonally blast the hatches to avoid the spikes.

The last part is the head. The weak spot is the laser mouth, which only opens when firing. The best weapon against the mouth is the Hornet Chaser, which will chase the laser even when closed. If it runs out, it's best to use the Laser Trident. The Black Hole Bomb can also be used, as it absorbs the lasers.

Trivia

 * This boss is, to a certain extent, similar to the U-555 miniboss in Duff McWhalen's stage in Mega Man X5.