Merman

Merman is of a sea tribe that have ruled the water world and have targeted the world above to conquer. They mostly stay under the sea, appearing in caves near the seashore from time to time. A male mermaid race that rules in the deep sea. Usually can be found in the deep sea or a seaside cave.

Ragnarok Online II
In RO2, there are 5 variations of this monster:
 * Merman
 * Merman Trooper
 * Merman Warrior
 * Merman Temple Guard
 * Merman Special Warrior