Widewater Lagoon is a 8.8-hectare (22-acre) Local Nature Reserve in Lancing in West Sussex.

[1][2] This coastal saline lagoon is separated from Lancing Beach by a man-made shingle bank.

The water is brackish and there are wildfowl such as herons and swans.

[1] A survey of the lagoon in 2013 found a wide range of flora and fauna including the rare water beetle Enochrus bicolor.

[3] There is access from Brighton Road, West Beach Road and via the footpath and cycle path running eastwards from Lancing beach green.