This is amazing work! Your colours and textures are superb, even the reflections/below surface look natural. Well, as natural as a giant KRAKEEEN can look. What breaks the dynamic of the picture is the man's blank expression. Maybe he's portrayed as his character is, but one would think that fighting a giant octopus would elicit some kind of facial action too.
The more I look at this, the more the style (especially of the character) reminds me of something else, a book or a game maybe, but can't figure out which one... -_-