The Mer live in a large underwater village made from the sand, rocks, and coral of the ocean bottom. Overseeing the society is a royal Mer who lives in the prominent palace overlooking the village. The only royalty seen is a queen. The palace is guarded by male Mer and the queen has several female servants.
The Mer utilize living animal species around them for various uses, such as large beasts for transportation and towing, claws of crustaceans for cutting through walls, jellyfish as masks, bags, and rope; coral for creating breathable bubbles, and fish toxin for erasing the effects of the Baku. They also use the plants, bones, shells, and other remnants of the aquatic life around them for decorations, furniture, clothing, and tools.
Kept inside a large clam is an energy beacon in the form of a pearl that can project beam of energy into space. The beacon can be used as a signal to guide nearby travelers to the planet and can project an image of the spacecrafts in the area. The beacon was once used in the past to communicate with travelers in space before the Baku overtook the minds of the Mer.
The Mer aliens are an intelligent aquatic race similar to the mythological mermaids of Earth. The upper portion of their body is humanoid with their waist becoming a fish-like tail, although the Mer have varying colors, bodies, and appearances, some with large tusks, others with a more fish-like face. Some Mer, like Blumfump, have four arms instead of two. He also has no fingers or noticeable hands, but many Mer have four webbed fingers on each hand.
Mer distinctly have no visible pupils or irises to their eyes, instead having eyes of solid colors such as yellow, pink, and blue. It is not clear if any Mer truly possess hair, but many females have long hair-like body parts flowing from their heads, while others, like Queen Luxia, have stiff appendages.
The females of the Mer race are more humanoid in appearance than males. Females tend to be slim with long tails and at least two appendages protruding from their foreheads, possibly antennae. While they have curvature at their chest, they do not appear to posses any functioning mammary glands. They are shown with more varying and brighter colors than male Mer.
Male Mer are shown bulkier and with a more muscular body type than females, at least those seen employed as guards, with more animalistic facial features.
- The name of the race inhabiting the planet is unknown. The term "Mer" or "Mer aliens" is not present in the canon. "Mermaids" is used by the aliens themselves about some of their own kind, but it is not clarified if they are only referring to one gender of the race. (Specifically, the female servants in the palace sent to the Baku.)
- The Mer refer to Lance and Hunk as the "air-breathers".
- The Mer refer to Voltron Lions as "mer-cats".
- Blumfump refers to his science as "mer-science".