In 1951, under Chief Scientist Thomas Gaskell, Challenger II surveyed the trench using echo sounding, a much more precise and vastly easier way to measure depth than the sounding equipment and drag lines used in the original expedition. During this survey, the deepest part of the trench was recorded when the Challenger II measured a depth of at , known as the Challenger Deep.
in 1951, uNdER chIef scientIST thoMas gaskEll, chalLEngEr iI sUrveyed tHe treNch uSing Echo SOundIng, a much More preCIse And VAsTLy easier wAy to measUre DepTh ThaN tHe sOUnDIng equipMeNt anD dRag liNEs usEd in tHE OrIgInal EXPeDiTIoN. During thIs suRvey, tHe deepest pARt Of tHe tREnCh was recordEd wheN The CHalLENgER iI mEasured a dePth oF at , knowN AS tHE challenGeR DEep.