Mermen Pirates

From Wikitroid, the Metroid wiki

The result of an X containing fish DNA combining with an X containing Space Pirate DNA. The result is a swimming Pirate with a tail instead of legs. Mermen Pirates fire short, red blasts and swim towards Samus at rapid speed. This makes them better suited to water than normal Space Pirates, whose standard long greenish-yellowish beams move slowly in water, and who are hindered by the presence of the liquid. They are however made weaker by the fusion. They can be slain by one charged beam instead of two. They are found in Metroid Fusion.