Voadam
Legend
A bunch of these do not match up to what I have seen in various D&D sources.Sea elves are magical fish people, merfolk are fully-committed fish-people, locathah are aquatic lizardfolk, sahuagin are fish-orcs and merrow are fish-gnolls. Tritons are simply water-people.
Sea elves are aquatic elves.
Koalinths are aquatic hobgoblins.
Locathah are straight out fish people.
Merfolk are fish centaurs.
Merrow are aquatic ogres, not gnolls.
Sahuagin have varied widely in their depictions, but traditionally have more HD and more intelligence than orcs.
Blackmoor page 21: "With a huge leech-like mouth, large reptilian eyes, and huge ear-like growths on the side of their heads they have an almost alien appearance. On the upper body are two arm-like extensions that act as forward fins and end in two pincer-like protrusions (opposed to each other) which are used to grasp tools and weapons. The main body is reptilian in nature, covered with thick hide and has a rudimentary tail which is used much like an alligator's tail for steering and propulsion. The two rear legs are located about 2/3 of the way down the body and are long and frog like, ending in a six-toed webbed foot which provides great stability when standing on soft sea bottoms and great propulsion when swimming."
Scrags are aquatic trolls.
Tritons are water elemental people, in 1e they have fish tails for legs, in 2e these turn into fin/flipper feet.