thats starting to look better huh?
the fish look a bit too bright, take down the brightness/lightness a bit
and you want to make them a bit blue/greener
in the hue/saturation you could infact mess with the individual colour channels, but thats getting a bit complex atm

oh, shadows, the fish arent shadowing on the seabed, im not so sure about how to do this, but maybe you could duplicate the fish layer, rotate the new layer 180degrees, drop the opactiy and make it black, not a great way, but thats how i would do it and maybe add some skew to it