Two issues at stake in this thread. Number one is the facts. During spring & summer marine plants grow prolifically in the intertidal zone & a spell of swell, as we have recently seen, pounds these brown coloured plants between the shore's mortar & the sea's pestle. I agree that from a distance one can imagine it to be a sewage slick but closer inspection reveals its true nature & I have taken doubters by boat to verify this. The raw sewage is there but has an entirely different appearance.
The second issue is the hypocrisy displayed by "green soap boxers". No doubt ante meridian ablutions were performed in the privacy of a bathroom & then the state of the sea complained about in web forums, as the plague species of the planet we humans have collective responsibility. The Mayor probably does not read this forum, if you really want your protest to count it would carry more weight if you were to do your daily dump on the town hall steps.