I think these are anaconda, and this’s some information about anaconda
Eunectes is a genus of non-venomous boas found in tropical South America, commonly called anacondas. An aquatic group of snakes inhabiting swamps and rivers, its members include some of the largest snakes in the world. Despite this, little was known about them until recently. The name Eunectes is derived from the Greek word Eυνήκτης, which means “good swimmer.” Three species are currently recognized.