The Darter is a large, slim water bird with a long snake-like neck, sharp pointed bill, and long, rounded tail. Male birds are dark brownish black with glossy black upperwings, streaked and spotted white, silver-grey and brown. The strongly kinked neck has a white or pale brown stripe from the bill to where the neck kinks and the breast is chestnut brown. Females and immatures are grey-brown above, pale grey to white below, with a white neck stripe that is less distinct in young birds. The Darter is often seen swimming with only the snake-like neck visible above the water, or drying its wings while perched on a tree or stump over water.

They take fish from local ponds. The Darter catches fish with its sharp bill partly open while diving in water deeper than 60 cm. The fish is pierced from underneath, flicked onto the water's surface and then swallowed head first. Smaller items are eaten underwater and large items may be carried to a convenient perch and then swallowed. Insects and other aquatic animals, including tortoises, may also be eaten, as well as some vegetable matter.