1975–1980 – RV "Thomas Washington" –– The Scripps Institution of Oceanography deployed the 1,490-ton Navy-owned, civilian-crewed research vessel "Thomas Washington" (AGOR-10) to the Mariana Trench on several expeditions from 1975 to 1986. The first of these was the "Eurydice Expedition, Leg 8" which brought Fisher back to the Challenger Deep’s western basin from 28–31 March 1975. "Thomas Washington" established geodetic positioning by (SATNAV) with Autolog Gyro and EM Log. Bathymetrics were by a 12 kHz Precision Depth Recorder (PDR) with a single 60° beam. They mapped one, "possibly two," axial basins with a depth of ±. Five dredges were hauled 27–31 March, all into or slightly north of the deepest depths of the western basin. Fisher noted that this survey of the Challenger Deep (western basin) had "...provided nothing to support and much to refute recent claims of depths there greater than ±." While Fisher missed the eastern basin of the Challenger Deep (for the third time), he did report a deep depression about 150 nautical miles east of the western basin. The 25 March dredge haul at encountered , which pre-shadowed by 22 years the discovery of HMRG Deep/Sirena Deep in 1997. The deepest waters of the HMRG Deep/Serina Deep at ± are centered at/near , approximately 2.65 km from Fisher's 25 March 1975 dredge haul.