I am no expert, but if you found it in the ocean, and it is relatively small (i may have missed it but I didn't see an indication of size) I think the skull is probably that of some type of sea bird. I don't see any teeth, a mammals teeth in the uppe jaw would almost certainly still be attatched.
However, birds have jaws that attatch far back on the skeleton, you can see the holes where the jaw hinged far back on the skull, and it is very possible that the beak was seperated right off the tip of the skull (closest to you in the pic)
in other words, I think what you have is the brain and nasal cavity, and ocular sockets, everything else is missing.
Conversely, there are some bony fish, and large ones at that, many larger fish have jaws that are independent of their skulls (like the barracuda) that is a possibility as well.
still think it's a bird though.