The UK's largest native breed of snake has been spotted swimming in the River Itchen.

Seen by near The White Swan pub in Mansbridge and Riverside Park, what is believed to be a grass snake was clocked slithering through the water.

The video was captured by Southampton resident, Andy Passey, and has caused a storm on Facebook with some residents stating they will think twice about going in the water after seeing the snake.

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The Hampshire Wildlife Trust has stated that grass snakes are most commonly spotted between April to October and is the biggest snake native to the UK - growing up to 1.5 metres in length.

According to the Hampshire Wildlife Trust: "the grass snake is usually greenish in colour, with a yellow and black collar, pale belly, and dark markings down the sides.

"Females are bigger than males."

Grass snakes do not bite and are completely harmless to humans - so residents taking a paddle at Riverside Park won't have to worry about falling prey to the harmless reptile.