This clip is composed of 150000 images utilizing focus stacking, due to the shallow depth of field involved with macro photography. Each frame of the video consists of 3 to 12 (!!) individual shots which were merged to extend the depth of field.  Only the introduction and the final scene are real-time footage.

Daniel Stoupin discusses Slow Life as well as the threats to the Great Barrier Reef that inspired him to make the video in a detailed entry over on his blog.