For several kilometres near the start of its course, the water flows into the Ease Gill Cave System, part of The Three Counties System, the longest cave system in Britain (and 26th longest in the world) via 14 major sink holes, to resurge at a major spring at Leck Beck Head.[1][2]
The rising of Leck Beck Head SD660 800 was dived extensively in the 1980s and required underwater digging and the use of an air chisel to make progress.[3] The overflow for this rising, Witches Cave (Yorkshire), has been dived through a 300m sump into Witches II. A dry entrance was dug into Witches II from the surface in 2010.[citation needed]