While both are aquatic races, there are key differences – merfolk are native to the Prime Material Plane, while Tritons hail from the Elemental Plane of Water. Tritons also prefer to stay in the depths, occupying deep trenches, while merfolk more commonly live in shallower waters where they can see still register day and night. And most significantly, merfolk have fishtails in place of legs, while Tritons are humanoids.