Hi Mark,
I don't really know that much cos I'm still pretty new to all this but I like them, especially the anemone fish (spelling could be terrible) and the close up of the blue spotted ray.
The main thing I'd say is you could bring out loads more colour from some of the pics that look quite blue. I'd suggest that you download Adobe's underwater action which you can do from this website
http://www.jackandsuedrafahl.com/download.html, the website has some other useful information on it too if you look around. This action sometimes makes the water look a bit of a purpley colour but is great on other photo's. I also like Picasa (free to download) this is really good for quick fixes to photos, this is particularly good if you aren't keen on spending loads of time fixing your photos.
Hope this helps.
Carly