Visibility was poor but I got this great video shot by swimming into the fabled Barracuda Tornado. I believe there were two groups converging into one massive swirl. That's over several thousand barracudas there. Being vicious predators, they are extremely dangerous but in this formation they seldom attack.
The video was taken at a depth of 4 - 7 metres with my FUJI F31D Camera. The sample you see is an edited low-resolution version of the original.