This is the sight today at our local break, between Gwithian and Godrevy. The brown in the sea is raw sewage, flushed into the sea via the river. It's a Combined Sewage Overflow. To quote the DEFRA site:
CSO spills contain rainwater and dilute untreated sewage, and are an important safety valve for the sewage system in storm conditions, helping to prevent flooding in homes and businesses. CSOs can spill into the sea, streams or rivers above beaches and in some cases close to bathing waters.
Swim in it (would you want to?) and you risk contracting a number of nasty ailments such as hepatitis. The pollution could take 12 hours to disperse. This needs to be addressed by the Water Authorities, but at least in this instance we were alerted to the pollution before we headed down to the beach, by the Surfers Against Sewage text alert service.
These alerts are only available for a small number of beaches at present and have been run this year on a trial basis by a DEFRA-led partnership called the Cleaner Seas Forum which includes SAS. There is a short survey available to fill in if you were lucky enough to receive any of these texts relating to beaches that you use. Please do take the few minutes to fill this in so that DEFRA can gauge how useful these texts have been and whether to extend the service nationwide. The link to the survey is below. Thank you. And thank you SAS for giving us the warning!