On January 27, 1990, during the third excavation attempt, the team of Norm "Jaws" Channing, Thom Engel, Patrick Lewis-Moors, Paul Rubin, June Skula, and Ben Zeller successfully hauled enough rocks out of the northernmost water pool in Clarksville Cave to permit entry into the hypothesized Lake Room conduit (Rubin, 1989).
Cave diver Norm Channing repeatedly filled buckets with rocks from the bottom of the lake. These were hauled up and disposed of far from the shore of the lake. One large limestone rock, measuring approximately 3.0 ft. x 2.5 ft. x 0.5 ft., was forcibly pulled from the lake. Its weight was calculated at 630 pounds. This rock had threatened to slide down the pool's floor and seal the constricted opening of the submerged conduit. Norm used virtually all 3000 psi of air from one of his 80 cubic foot capacity scuba tanks when completing the underwater rock removal. Fortunately, a second 80 cubic foot tank was on hand for the initial dive push.
At the time of the breakthrough, high surface and subsurface streamflow, resulting from snowmelt of the previous day, was declining. Osborne Cave was still overflowing from the larger than normal discharge rising from the newly exposed Lake Room conduit. The increased discharge was favorable for both rock removal and the subsequent dive push, as it quickly flushed disturbed sediments downstream. This resulted in excellent visibility underwater. Entry into the exposed conduit was made through an irregularly shaped constriction at a depth of 10 feet below the surface of the lake (see Figure 1). The toothed appearance of the constriction led team members to dub it the "Jaws of Death". Norm entered this feet first, pulling his tank through behind him. Once past the constriction, the passage's cross sectional dimensions opened up to approximately 5 feet wide by 6 feet high. A maximum depth of 18 to 20 feet was reached during the dive. Norm reports that the underwater conduit maintained a linear trend slightly east of magnetic north.
Two enlarged passage segments were found during the dive push, one at 80 feet and the other at 180 feet. A bedrock pillar, spanning from floor to ceiling, splits the passage in the first enlarged segment.,, The qastern and western walls of this area require further investigation. The second enlarged passage segment, "The Channing Chamber", measures approximately 12 feet long, 5 feet wide and 8 feet high. Half of this chamber is air filled, the only air filled portion of the Lake Room conduit thus far encountered.