Umibozu

Umibozu are a race of giants living underwater. So far, the only known umibozu is Wadatsumi (though it is extremely likely that Sanjuan Wolf is one as well).

Appearance
Umibozu are a very large species, towering over regular giants and almost the same size as the Kraken. The only known umibozu, Wadatsumi, has a human-like appearance with a more ovular face and a hairy body.

Overall Strength
They are an incredibly powerful race due to their enormous size. Wadatsumi can beat a huge fish, several times bigger than Thousand Sunny, with one punch. But he was defeated by the Kraken easily.

Trivia

 * Umibōzu (海坊主?, "sea boze") is a spirit in Japanese folklore living in the ocean.