Seto no Hanayome.) It premiered in Japan back in 2007 and lasted twenty-six episodes and two direct to video OVAs. It's currently available here (in its entirety) as two DVD sets.
The premise of the show is the boy, Nagasumi, is saved from drowning by a cute mermaid named Sun. Because he saw her as a mermaid he must marry her or she will die. And there to make sure he does the right thing is her crazy family. Even though this is a show about mermaids it comes off more as a mafia/yakuza show (her family reminds me of Lums family in Urusai Yatsura.)
Being a comedy there are of course lots of zany characters and slapstick comedy which might not be your thing but it's worth checking out. You can watch the entire series (except the OVAs) here on hulu.