A six-year hiatus ensued while open circuit air diving became established, along with free-swimming and the use of neoprene wetsuits. The new generation of cave diver was now more mobile above and under water and able to dive deeper. Using this approach, Dave Savage was able to reach air surface in the 18th chamber (chambers did not have to have air spaces to be so named; they were the limits of each exploration) in May 1966. A brief lull in exploration occurred while the mess of guidelines laid from the ninth chamber was sorted out before John Parker progressed first to the large, dry, inlet passage of the 20th chamber, and thence followed the River Axe upstream on a dive covering at a maximum depth of to the 22nd chamber where the way on appeared to be lost.