The color pattern consists of olive green background overlaid with black blotches along the length of the body. The head is narrow compared to the body, usually with distinctive orange-yellow striping on either side. The eyes are set high on the head, allowing the snake to see out of the water while swimming without exposing its body.
Anacondas live in swamps, marshes, and slow-moving streams, mainly in the tropical rainforests of the Amazon and Orinoco basins. They are cumbersome on land, but stealthy and sleek in the water. Their eyes and nasal openings are on top of their heads, allowing them to lie in wait for prey while remaining nearly completely submerged.
The primarily nocturnal Anaconda species tend to spend most of its life in or around water. Anacondas are also sometimes known as the water boa; they spend more time in water than any of the boas. They seem rather slow and sluggish when traveling on land due to their size, although they have the potential to reach high speeds in the water. They tend to float beneath the surface of the water with their snouts above the surface. When prey passes by or stops to drink, the anaconda will strike (without eating or swallowing it) and coil around it with its body. The snake will then constrict until it has suffocated the prey.
Primarily aquatic, they eat a wide variety of prey, almost anything they can manage to overpower, including fish, birds, a variety of mammals, and other reptiles. Particularly large Anacondas may consume large prey such as tapirs, deer, capybaras, caimans, and even jaguars, but such large meals are not regularly consumed. The Green Anaconda's eyes and nose are located on the top of the head, allowing the snake to breathe and watch for prey while the vast majority of the body is hidden underwater. Many local stories and legends report the Anaconda as a man-eater, but little evidence supports any such activity. They employ constriction to subdue their prey. Cannibalism among Green Anacondas is also known, most recorded cases involving a larger female consuming a smaller male. While the exact reason for this is not understood, scientists cite several possibilities, including the dramatic sexual dimorphism in the species, and the possibility that a female Anaconda requires additional food intake after breeding to sustain the long period of gestation. The nearby male simply provides the opportunistic female a ready source of nutrition.