A6000, what else do I need to start?

DigiPainter wrote:

So say I shoot something underwater and it turns out all blue, like a school of big predator fish, if I shoot in raw I can bring some colour back to the fish?

You find something in the photo that can serve as a reference grey point - a patch of sand or rock, another diver's tank, etc - and click on it with the spot white balance picker tool. If you don't have anything to serve as a white balance reference, take another shot taken under similar conditions and copy/paste the white balance from there.

Sorry I was thinking of the sigma 60mm f2.8 with a diopter. But looking at prices the 50mm f1.8 sony might be a better go.

Neither of those will work as a macro lens, and diopters are a kludge - they leave you with a very short working distance window; throwing example numbers, you might be able to focus no closer than 4cm and no further than 6cm - if you need to be 10cm away to properly frame the subject, then tough luck.

So essentially you have 2 setups, flat port for shooting clioseups/macro
Bulb port for shooting wide angles and fish eye?

Right. I shoot a Sony 10-18mm f/4 behind an eight-inch dome port and a Sony 90mm f/2.8 macro behind a flat port. For special occasions, I have a 7Artisans 7.5mm fisheye behind a four-inch dome port. An alternative to this would be a 16-50mm zoom behind a flat port, with a wet wide lens for wide-angle (a Nauticam WWL-1 will give you 130 degrees diagonal FoV) and a diopter for macro.