These are among the most challenging underwater images to capture.
On this snorkel I set out just to shoot under overs and this is the only decent one from 80 or so.
This is what I learned....
Need glassy calm, shallow, clear water
Must have a big dome port (8" Ike)
Use the widest lens you have (Sigma 15mm, but wider would have been better. I actually came home and ordered a Tokina 10-17mm soon after)
f/9 is not enough for sharp above and below, need more like f/16
Shoot manual exposure just making sure not to blow out above water highlights. RAW helps a great deal and the graduated filter in CS5 Camera Raw works wonders.
Focus on the underwater detail and lock focus it for the shot.
To reduce water drops in the image, spit on the dome and rub the saliva around the top half.
Start with the dome fully submerged then take the shot within seconds of lifting it up and framing.
