From Ardrana

Sahuagin are a vicious, predatory race of fish-men that live in warm coastal waters. They are highly organized and greatly enjoy raiding shore communities for food and sport.

Typical sahuagins are blackish green on their backs, shading to green on their bellies, with black fins. Their great, staring eyes are deep, shining black. They have scaly skin, with webbed fingers and toes, and their mouths are filled with sharp fangs. About 1 in 216 sahuagin is a mutation with four usable arms. These specimens are usually black shading to gray. Females are indistinguishable from males, except that they are slightly smaller. Hatchlings are a light green color, but they darken and attain full growth approximately one to two months after hatching.

Sahuagin are fairly common in the coastal regions of Ardrana, especially in and around The Grinder.

Note: Sahuagin originally appeared in this form in the 2nd Edition Monstrous Manual for the AD&D game from TSR. Their use here is for the purposes of providing context for the campaign only.