The African Darter Anhinga rufa differs from cormorants by its very slender, long neck and head, as well as its long pointed bill. When swimming, only the long neck and head are visible, which is why it is often referred to as 'snakebird'. It often glides in flight, with broad wings and a long, broad tail.
Darters are also common residents of lakes, dams and slow-moving rivers; rarely coastal lagoons and estuaries.
Which makes this a Cormorant, based on location and general characteristics.
The bird family Phalacrocoracidae is represented by some 40 species of cormorants and shags. These medium-to-large sized sea-birds are coastal rather than oceanic birds, and some have colonised inland waters - indeed, the original ancestor of cormorants seems to have been a fresh-water bird, judging from the habitat of the most ancient lineage. They range around the world.
All are fish-eaters, dining on small eels, fish, and even water snakes. They dive from the surface, though many species make a characteristic half-jump as they dive, presumably to give themselves a more streamlined entry into the water. Under water they propel themselves with their feet. Some cormorant species have been found, using depth gauges, to dive to depths of as much as 45 metres.
After fishing, cormorants go ashore, and are frequently seen holding their wings out in the sun. All cormorants have preen gland secretions that are used ostensibly to keep the feathers waterproof.
Cormorants are colonial nesters, using trees, rocky islets, or cliffs. The eggs are a chalky-blue colour. There is usually one brood a year. The young are fed through regurgitation. They typically have deep, ungainly bills, showing a greater resemblance to those of the pelicans', to which they are related, than is obvious in the adults.
http://simplyclover.tumblr.com/post/7805069471/this-cormorant-was-preening-prior-to-drying-in-the
Sources: Wikipedia and observation
