Merman

Mermen are mythical male equivalents and counterparts of mermaids – legendary creatures who have the form of a male human from the waist up and are fish-like from the waist down, having scaly fish tails in place of legs. A "merboy" is a young merman.

Mythology
In Medieval Europe, mermen were sometimes held responsible for causing violent storms and sinking ships.

In Cornish folklore into early modern times, the Bucca, described as a lonely, mournful character with the skin of a conger eel and hair of seaweed, was still placated with votive offerings of fish left on the beach by fishermen. Similarly vengeful water spirits occur in Breton and Gaelic lore which may relate to pre Christian gods such as Nechtan.

In Finnish mythology, a vetehinen, a type of Neck, is sometimes portrayed as a magical, powerful, bearded man with the tail of a fish. He can cure illnesses, lift curses and brew potions, but he can also cause unintended harm by becoming too curious about human life. The boto of the Amazon River regions is described according to local lore as taking the form of a human or merman, also known as encantado ("enchanted one" in Portuguese) and with the habit of seducing human women and impregnating them. Chinese mermen were believed to only surface during storms or, in some cases, were believed to have the ability to cause storms.

Characteristics
The actions and behavior of mermen can vary wildly depending on the source and time period of the stories. They have been said to sink ships by summoning great storms, but also said to be wise teachers, according to earlier mythology. Mermen, just like mermaids, can lure and attract humans with their enchantingly beautiful, soft melodic and seductive siren-like singing voices and tones.

Appearance
Warrior mermen are typically seen carrying spears they use as weapons to attack and kill their enemies.

Merpeople have a noticeable sexual dimorphism in terms of their aquatic forms. While mermaids and mermen share the same scaly upper bodies, fangs, claws, webbed hands, webbed underarms, a pair of small fins right above the caudal fin, and dolphin/whale shaped caudal fins, their tails and back fins are noticeably different in appearance. Mermen, unlike mermaids, have slightly longer tails, larger caudal fins, three or four pairs of fins shaped like those of dolphins, whales, or sharks running down their back, with an additional one positioned in the middle of the buttocks where the crack would be. Their tails also have dolphin/whale/shark-like fins along their tails in three pairs. One pair sticking out behind the thighs, one pair sticking out around the knee area, and of course a pair above the above the caudal fins similar to the females. Mermen caudal fins lack the stinger that mermaids have.