Police warned this week young people were taking their lives into their hands while swimming in flood water at Lewes Railway Land.
Posters are being put up around the nature reserve after concerns were raised people were playing in the flood water and filming it.
Sussex Police are putting up warning notices about the danger of swimming there, such as infections that could be contracted from the polluted water and hidden dangers under the surface such as branches, deep holes and undergrowth.
PCSO Julie Whittaker-Jones said: “Please take care around the flood water. Don’t take your life in your hands by going into water that you can’t see through.”
If you’re worried about flooding or need advice you can contact the Environment Agency’s Floodline on 0345 988 1188 or 0845 988 1188 (24 hour service).
The type talk number for this service is 0845 602 6340.