ambush-predators anaconda aquatic boa-constrictor capable-swimmer coil coiling common-anaconda constrict constricting constrictive crush crushing distinctive-color-pattern enclosure eunectes-murinus green-anaconda heaviest heavy-bodied-snake large long nocturnal rainforest reptile reptilian rivers shelter sheltered snake solitary squeeze squeezing variable-color-pattern water-boa balls bawls marble round stone