Seto no Hanayome appears to be a harem anime where the harem consists solely of a mermaid who's the heiress to a yakuza family and a guy with an afro. It also has a giant octopus. I can think of no higher recommendation for an anime.

(Disclaimer: I do not know if I am recommending this anime, because I don't have any plans to see past the first two episodes. But doesn't it sound awesome?)