Thanks Pete - I've downloaded it. Southern Water has a BeachBuoy app which is set up to do the same thing, however, sometimes it's questionable. At the moment it seems to agree with the SAS one, but I have heard that occasionally some of the monitors seem to be 'out of action'.
I’ve had the Saferseas app for about a year and it’s useful for sea swimmers,boarders and kayakers although if you abandoned activities every time a notification of a dump came up you wouldn’t go anywhere but it does localise it. It’s a bit depressing to see how many dumps there are even when there’s no rainfall.