This shows the pattern the tail fin makes as they are getting airborne. It looks like they get quite a boost from the tail as they start off. This happens so quickly I did not even notice it until I looked at the photos. In the adjacent photo in the series, note how the lower lobe of the caudal (tail) fin is elongated--clearly this helps during the takeoff!  Cheilopogon_melanurusPCCA20070623-3954A