Surume

The Kraken is a massive octopus creature from Norse mythology. The Straw Hats first encountered one on their way to Fishman Island. Apparently they feed on ships. Caribou recites a story about it, calling it "the enemy of the human race". Luffy apparently doesn't consider the one they encountered a threat, as he said he is going to tame it and refers to it as "that little guy" - despite the fact that the Kraken in question is at least several hundred times larger than the Thousand Sunny.