I came across these guys when visiting Lamplighters Marsh, Shirehampton, Bristol (Nr the mouth of the River Avon) They are members of Shirehampton Yacht Club, and, each Saturday, meet to clear mud of the old slipway. This used to be the slipway for Pill Ferry. Now it is used for launching the club’s boats. In the past the slipway was level with the bank and kept clear of mud  by the flow of the tides. Now the banks have been built up on either side of the slipway (partly for flood defence) and each tide drops a lot of mud on it. It very quicky becomes unusable unless a rolling programme of clearing is maitained.