Mermaids are enemies that appear in Risky's Revenge, Pirate's Curse, Half-Genie Hero, and Shantae and the Seven Sirens. Oddly enough, they aren't encountered underwater at all throughout the series. They wield tridents that shoot large water bubbles at Shantae, and sometimes they just blow kisses. Mermaids are also quite durable and take quite a few hits before they go down.
They become tougher by shooting five water bubbles at once in all directions, making it much harder to avoid up close. The mermaids also have a queen. They stop attacking when Shantae frees their queen, and are replaced with Nagas.
Shantae and the Seven Sirens
For whatever reason, the Mermaids are attacking Shantae again. They can be found all over the island, with the same attacks as in Half-Genie Hero.
Their Monster Card doubles Shantae's swim speed in human form when equipped.