Piranha: Ocean Adaption

Piranhas are herbivores. they thrive in shallow, warm, FRESH water. I changed the piranha to be an ocean dwelling creature. An ocean adapted piranha would have to develop larger kidneys to produce highly concentrated urine and conserve water in a salty environment. Its body would become smaller and more streamlined for faster swimming, while dull browns and blacks would help it blend into rocky sea floors. Enlarged gills with extra chloride cells would regulate salt and improve oxygen intake. Its enlarged eyes and stronger jaw would help make it an efficient hunter in a more competitive environment.