When we visited the Amazon Rainforest in Peru, our local guide retrieved a green anaconda from a stagnant pond for us to take a closer look at this well-known reptile. Anacondas are good swimmers with eyes and nostrils at the top of their heads. Ponds and rivers are a great place for these snakes to stalk prey—or to hide from predators. They are the biggest snakes in the world— non-venomous constrictors that swallow their prey whole. Here at the Philadelphia Zoo, the green Anaconda peeks at us from behind the leafy curtain in his habitat.