This is a young one, so retains the bright colours that make this snake so attractive.
All of this information, and more, can be found over at our sister site www.hongkongsnakeid.com which contains a comprehensive list of snakes in hong kong and great photos, along with their key details and facts.
This snake can be found https://www.hongkongsnakeid.com/mountain-water-snale
PREVALENCE: Not common
ACTIVE PERIOD: Mostly active at night
KEY ID FEATURES: Light brown or olive body with dark brown and yellow/white vertical banding, 70-110cm long
BEHAVIOUR: Aquatic, may be found in slow or swift move streams, catch waters and pools
OTHER: Aggressive if handled, will bite readily
Mountain Water Snakes are light brown or olive green with black and whitish yellow vertical bands running the length of the body. The bands may be faded in adults along the spine but are well defined on the sides. Characteristic rusty orange to pink coloration between the bands on juveniles which fades as they reach maturity. A slender species when mature and can grow between 70 and 110cm. Round pupils and a medium sized head and jaw relative to body size.
Mostly nocturnal Mountain Water Snakes come out at night to hunt fish and occasionally amphibians. They have also been observed out during the day in both early morning and at dusk. Quick to bite, musk, roll and squirm excessively but despite being aggressive they are not considered dangerous to humans.
(use this link for a video : https://youtu.be/h-NrlxHtznw)
Found largely in the New Territories the Mountain Water Snake is a less common snake to encounter in Hong Kong. Due to their diet of fresh water prey they can be found most readily near slow or swift moving and cascading mountainside bodies of water.