Photographs similar to this are the goal of many whale photographers. The whale tail only pops out of the water when the whale is on its way down, diving deep into the ocean to feed on plankton.
The whale tail coming up and out of the water happens much less often than the more common breaking the surface for air and feeding near the surface. Seeing the tail out of the water like this indicates the whale is diving down deep to feed. All the photographers set their camera to motor drive and press the shutter down time after time and get no sign of a tail. One in 20 sightings, or so it seems, result in the whale fluke rising out of the water.