If the government really wanted this to stop, it could stop them.Seeing as the UK government can make it a crime to protest in"annoying" ways, it could, it could clearly make it a crime, punishedby imprisonment, to intentionally pollute the waters.
So why doesn't it? I speculate that it is a matter of values. Underplutocratist rule, letting the "investors" extract money they aresupposedly entitle do takes priority.