U-555

U-555, known as Death Avenge (デスエベンジ) in Japan, is the sub-boss of Duff McWhalen's stage in Mega Man X5, a giant whale Mechaniloid that belonged to a marine museum and was affected by the Sigma Virus. It chases the player in the stage three times, each attacking with a different part: The first part is its head, which releases Dejira GR and lasers from its mouth. The second part is the tail with four missile launchers. The third part is the upper part of its body, where its core is located.

Trivia
The "Shark Submarine" from Mega Man 9 is similar to this boss.