A stretch of beach and the shallow water off it, with gloves, bags and water provided. Two and a half hours, open to anybody, and children come with a parent who stays.
Everything collected is weighed before it goes to the waste site, and the figures go into a record we hand to the island council using the same categories every time. Over two years that record tells a council whether a stretch is getting better or worse, which is the only thing that makes a morning of picking up bottles worth anybody's Saturday.
The shallow water part is optional, supervised by two adults who can swim, and nobody goes past their waist or dives for anything. We have turned down three requests to run a dive clean up, because we are not equipped to supervise one and somebody drowning at a charity event is not a risk anybody here will carry.