I totally dig this, if you want some lowly opinion like mine on what to improve...I think it'd be cool to have some clouds by the birds, so there isn't so much empty space, but I would totally wear this.
(Suggestions on improvement: I'd consider more details on the whale fins and backs--I know they are probably based off humpbacks because of their distinctive shape, but a little detail in a thinner line weight--the barnacle-bumps, the speckles, the bumpy fins, etc. Also I'd consider some transitional elements between the sky and water.)
About my design
I hope you like it.