- “We are not the Sirens. We are the merfolk. We sing our own melody and we do the bidding of the Sirens.”
- ―Morveren, Aquala and Aquila to Jack Sparrow
Merfolk, also known as the merpeople and sometimes referred to as Scaly Tails, were mythical creatures of various legends and lore, known to be half human and half fish. The merfolk of Isla Sirena, the majority of them being mermaids and one known merman, served as agents of the Sirens, dragging many sailors down to a watery grave.
The mermaids of Isla Sirena were part of the merfolk that did the bidding of the Sirens, who were in turn ruled by Davy Jones. They resided in chambers within Isla Sirena, and had control over various creatures that inhabited Davy Jones' Locker, including iguana monsters and sea beasts. The merfolk also had contact with Tia Dalma, and were aware of legendary artifacts such as the Sword of Cortés.
There were at least three separate sub-species of merfolk in Isla Sirena, distinguished by the color of the scales on their fish-like tails. Those with green tails were analogous to soldiers, and operated as the military arm of the society. They confronted sailors lured to Isla Sirena and dragged them down to the island itself. Red-tailed merfolk were the servants of mermaid society, and were commonly found wading around waiting for orders. They acted as guards and workers in Isla Sirena. Finally, blue-tails served as the leaders of the mermaids. The three blue-tails encountered by Jack Sparrow, Morveren, Aquala and Aquila, were named as "chairwomen" by the green-tails. Tonra was the only known merman in the merfolk species