Homalopsis buccata
Diet
Fish such as tilapia, catfish and Asian swamp eels, plus frogs and freshwater crustaceans
Range
Tropical South-east Asia, from northern Sumatra and Borneo to the Malay Peninsula and extreme southern Thailand
Litter size
2-20 live young, averaging about 9
Size
Usually about 1m
Linne's water snake, the puff-faced or masked water snake, Homalopsis buccata, is a mildly venomous water snake usually about 1m long, with a banded pattern and an anaconda-like body shape. It subdues fish, frogs and freshwater crustaceans with mild venom from a grooved rear fang rather than by constriction (Wikipedia, general species account).
It is ovoviviparous, with females bearing 2 to 20 live young, averaging about 9, and breeding all year. Linnaeus described it in 1758. The source places it in tropical South-east Asia and does not mention Nepal, so its Nepal status should be checked (Wikipedia, general species account).