Walking on water

At the Great Western Dockyard in Bristol where Isambard Kingdom Brunel's SS Great Britain is on display. After being rescued/salvaged from the Falklands (or Islas Malvinas if you prefer) in 1970 her iron hull continued to corrode in the humid atmosphere of the dock in Bristol. The solution to this was glass plate installed at the level of her original waterline and dehumidifiers to keep the space beneath dry enough to prevent further corrosion. These guys are wandering around in a couple of inches of water brushing away in an effort to get rid of the algae that grows on the glass.