A 21-year-old woman has been bitten by a shark, after walking in knee-deep water in the Aparima estuary near the Riverton rugby grounds, about 2am yesterday (18 Dec).

She received a significant laceration to her leg that required treatment from emergency services.

The shark is suspected to be a sevengill.

Police are asking anyone heading into the water to be conscious of the environment, follow safety guidelines and avoid late-night swims.

Water Safety NZ has resources and advice for all water-going holidaymakers.