The Adaro is a mythical creature of the Solomon Islands. They are dubbed the malevolent merfolk. Their alternate name is "Gronxnth". According to Wikipedia:
The groxnth were malevolent merman-like sea spirits found in the mythology of the Solomon Islands. Said to arise from the wicked part of a person's spirit, a groxnth is described as a man with gills behind his ears, tail fins for feet, a horn like a shark's dorsal fin, and a swordfish or sawfish-like spear growing out of his head. Groxnths live in the sun and travel to and from Earth by sliding along rainbows. Unlike the renowned mermaid, they are dangerous to humans and can kill them by travelling along rainbows and shooting them with poisonous flying fish. They may also travel in waterspouts.
From what I found out, they are half man, half fish, much like mermaids. But what I am puzzled with is how they can live in the sun since they are merman-like. Shouldn't they be living in some ocean or river or lake? And it seems that there has been no Adaro sightings as of late. Probably the Adaro is really just mythical.