On Scripps Institution of Oceanography's "INDOPAC Expedition Leg 3", the chief scientist, Dr. Joseph L. Reid, and oceanographer Arnold W. Mantyla made a hydrocast of a free vehicle (a special-purpose benthic lander (or "baited camera") for measurements of water temperature and salinity) on 27 May 1976 into the western basin of the Challenger Deep, "Station 21," at at about depth. On "INDOPAC Expedition Leg 9", under chief scientist A. Aristides Yayanos, "Thomas Washington" spent nine days from 13–21 January 1977 conducting an extensive and detailed investigation of the Challenger Deep, mainly with biological objectives. "Echo soundings were carried out primarily with a 3.5 kHz single-beam system, with a 12 kHz echosounder operated in addition some of the time," (the 12 kHz system was activated for testing on 16 January). A benthic lander was put into the western basin (, on 13 January, bottoming at and recovered 50 hours later in damaged condition. Quickly repaired, it was again put down on the 15th to depth at . It was recovered on the 17th with excellent photography of amphipods (shrimp) from the Challenger Deep’s western basin. The benthic lander was put down for the third and last time on the 17th, at , in the central basin at a depth of . The benthic lander was not recovered and may remain on the bottom in the vicinity of . Free traps and pressure-retaining traps were put down at eight location from 13 to 19 January into the western basin, at depths ranging from to . Both the free traps and the pressure-retaining traps brought up good sample amphipods for study. While the ship briefly visited the area of the eastern basin, the expedition did not recognize it as potentially the deepest of the three Challenger Deep basins.