The following presents new data collected as part of a recent Historic Scotland funded project – the Scapa Flow 2013 Marine Archaeology Survey – which aimed to assess the extent and condition of some of the sites around Scapa Flow.
Laid down during World War I, the hurdles were installed to control shipping access to Scapa Flow. Historical photos show that while in use the hurdles protruded from the water at all states of the tide. The height of the structures was reduced by an icebreaker in 1920 to facilitate shipping. The hurdles are situated in the middle of the channel in strong tide and current and though possible, diving on the clestrain hurdles is not recommended.