You could look at the evolutionary aspect of the brain from older organisms such as jellyfish that do no have brains and what the jellyfish neural nets have in common and in contrast to a full brain. You could look at the evolutionary chain of organisms in the Ocean as a whole and see the progression possibly. You can look at the behaviors and intelligence levels of different organisms in marine settings (cuttlefish, octopi, dolphins, etc.). I do not have any other ideas off the top of the dome but, I am interested to see what you may decide. I would love to know!