Mermaids can breathe underwater and in the air and they can move on land as well. With their tails, they can swim very fast throught the water and like mermen, they can talk perfectly clear underwater.
Mermaids are very beautiful and can enchant people with their beauty as when Slippery Pete fell into the water, he instantly fell in love with two minor mermaids.
Mermaid tears turn into candy that they store in their hearts. This candy can grant any wish but it costs the life of the mermaid the tears came from.
Mermaids can transform into skymaids after someone has used all their wishes.
Mermaids are shown to have some power over the ocean, shown when the Mermaid Queen sucked all her mermen guards into a whirlpool and then she, herself emerged from the whirlpool. Also, when the Mermaid Queen was dying, she caused a terrifying storm.