Looking like a good start already! A couple of things pop out at me, in no particular order:
- in some shots your focus is soft. This looks to be like you are inside the range of the lens (the purple coral head & maybe the head of the eel)) or the camera has locked on to something other than the subject's eye (the cod & maybe the eel).
- looks like the strobe needs to be adjusted a little bit. In some shots you are getting lots of light in front of the subject but then it falls off without lighting the whole subject properly (cod, the lobster & the ship part above him; again, perhaps the eel too as he doesn't seem to have been lit). On the sea star, the light is only catching the edge of the star. Strobes can be tricky to get right - one reason why shooting digital is great...take the shot, review the shot, adjust the strobe; usuallly it's just a tiny movement.
- for wide, far shots (like the bottom wreck), I'd be tempted to turn off the strobe and go for a monochrome shot. It will eliminate any backscatter and give you a great place to start to go black and white. If there was a fabulous element in the foreground, I'd light that with the strobe and have the light fall off the rest of the subject...but I'd shoot it both ways!
The shark is gorgeous. I love the crispness of his fins and the view from underneath. The diver shot is nice too - I'd probably crop to vertical. When you're under, try flipping the camera vertical, too. There are a ton of subjects that suit a vertical format and sometimes it can make a ho hum shot really special!
I hope that helps. After all that, I think you are doing great and that the more you dive, the better your shots will get!
