Cradle Hole Cave. On reaching the downstream end of the cave, they discovered that water levels were now low enough to see a series of low arches above the water surface. By anchoring a floating candle part-way through the passage, exiting the cave and returning to the end of the Grand Gallery in Marble Arch Cave, the cavers confirmed that the passages were connected; subsequently, two of the party swam through to make the first through-trip between Marble Arch Cave and Lower Cradle Hole Cave. 1966–1967: Skreen Hill 2, 3 and Legnabrocky Way By the mid-1960s a number of advancements had been made in cave diving, by which method speleologists had extended their explorations into caves beyond the sumps that would normally have halted progress. In December 1966 divers Dave Cobley and Mike Boon made preparations to dive Sump 1 in Skreen Hill passage. Before making the dive however, they investigated a small dry passage leading off on the left bank of the lake, finding it to be blocked at the end by unstable boulders in the roof. The cavers removed one of the boulders to reveal a way on, which led via a dry route to the far side of Sump 1. The new section of river passage beyond was named Skreen Hill 2, and a further inlet passage was named Legnabrocky Way. A notable feature of the Legnabrocky Way is the Giant's Hall, a large chamber 60 m long, 30 m high and 15 m wide (200×98×49 ft). Despite only carrying a small stream, the Legnabrocky Way is the largest section of passage in Marble Arch Cave. The upstream continuation of the river in Skreen Hill 2 was found to be shortly blocked by Sump 3, so in March 1967 a team of divers returned to attempt further exploration. William Frakes and John Ogden were the first to successfully pass the sump to reach Skreen Hill 3, of "magnificent stream passage" ending in boulder choke. In the ensuing months a comprehensive survey was made of all of Marble Arch Caves, including the newly discovered sections. During this time, surveyors learned of the deaths of Frakes, Ogden and Colin Vickers—another of the divers in the original team—in the Mossdale Caverns accident. In tribute, a number of cave features in Skreen Hill 3 were named after the three cavers. 1982–1985: show cave development From 1982 until after opening in 1985,