Very nice shape design and I like you water aesthetics (reminds me of mine ;D ). The sense of motion and life in the drawing is pretty nice too, and the use of blue for the shadows(and not just a darker peach) shows that your delving at least somewhat into how color affects the mood and atmosphere of a piece.
Some things you might want to change are:
1) adding more cohesiveness to the drawing. You've shaded the character, but the water, board, and sail are all flat looking, which makes it look like you done a half drawing half graphic (and the two together are difficult to pull off in tandem). Try adding some sort of shading to the BG elements (it'll help give the drawing more life and more depth too!)
2) Figure to ground- right now (though by the boards shadow on the water I imagine hes in the air atm ) it doesn't feel like your windsurfer in actually ON the board, it feels ambiguous
3) You might want to try and push varying line weight, a lot of the minor details look a little strange and are competing in the hierarchy of your piece.
Even if this piece is done, just keep them in mind for our later ones~