The anhinga first spears a fish while swimming underwater. Next it
rises to the surface and tosses the catch into the air. Note that the
fish will be oriented properly for swallowing. If the anhinga doesn't
get it right the first time, it will toss the fish repeatedly until it
is oriented for head-first swallowing.
In answer to some questions:
This photo was taken at a small urban lake in northern St. Petersburg, Florida (behind Ed White Hospital). I have taken similar photos at several other locales. The technique in getting the shot is always about the same. The challenge in getting a shot like this is to first locate a "fishing" anhinga and then anticipate where it might pop back to the surface. They are capable of swimming considerable distances underwater. As soon as I see a disturbance on the surface of the water I try to focus on it. When the head rises above the water, I usually can see if the anhinga has speared a fish. It tosses and eats the fish in a second or two usually so timing is critical. This is the same species that is called a "darter" in some areas.
This photo was chosen for the 2008 North American Nature Photography Association's annual Showcase.