Never forget that flash is just another light source, and for it to work in your favor, you must do your best to allow ambient light to do its part. Without allowing available light into the frame, the sense of place is gone. We want to see the blue in the water and the environment these creatures thrive in.
Remember to adjust the power of your strobes based on the subject. When photographing fish that are too close or highly reflective, take your strobes to 1 2 or 1 4 power. Dont point your units directly at the subject This illuminates the water between your lens and the creature, creating backscatter.