I just watched Azorian, The Raising of the K-129 - outstanding and I have a new appreciation of the history the HMB-1 barge.
Thanks for the comment! We learned quite a bit about the HMB-1 and its workings during the research for the documentary film & subsequent book.
Similar to a submarine, the HMB-1 was built with large ballast tanks; but the compressed air was supplied by hoses from support ships. The role of the barge in Project Azorian was to serve as a secure site for construction, testing, and transfer of the actual Lockheed built device (Capture Vehicle or CV) used to grasp the wreck of the K-129. The HMB-1 was parked at Redwood City, Ca. while the CV was assembled and tested inside the barge. Once ready, the barge with the CV was towed out to Santa Catalina Island, just off Avalon, and submerged in roughly 160 feet of water on the flat sandy bottom. The Glomar Explorer (HGE) was then positioned carefully above the barge. The HGE moonpool doors were opened as was the sliding roof of the HMB-1. The two docking legs on either side of the moonpool were lowered, and engaged pins (big, 3 foot diameter pins) at the ends of the CV. The CV was then lifted into the HGE, moonpool doors closed and the HGE moved off. The sliding roof of the now empty HMB-1 was closed and HP air pumped into the HMB-1 ballast tanks. After surfacing, the HMB-1 was towed back to Redwood City. To recover the CV after the mission, the process was reversed.
Contrary to some published accounts, the HMB-1 never accompanied the HGE out to the mid-Pacific site during the attempted recovery of the K-129. HMB-1 was never designed to sink to 16,400 feet, which was the depth of the K-129 wreck. Below is a still from the film of the CV being lifted out of the HMB-1 into the Glomar Explorer off of Santa Catalina. Click to enlarge.