DSSV Pressure Drop used a Kongsberg EM124 multibeam sonar to survey the Puerto Rico Trench in 2018.
The survey formed part of the Five Deeps Expedition’s effort to map the deepest locations in all five oceans. In December 2018, the 225-foot support vessel carried the EM124 on a gondola mounted beneath its hull while surveying the Brownson Deep area of the Puerto Rico Trench.
A multibeam echosounder sends acoustic pulses across a broad swath of seafloor and measures their return time, producing detailed bathymetry. The EM124 was designed for full-ocean-depth work and helped identify the trench’s deepest point before Victor Vescovo’s crewed descent in the submersible DSV Limiting Factor.
The main confusion is between survey systems and unrelated ocean instruments. Simrad EK80 is principally a scientific echosounder, while Hydrosweep DS and SeaBeam systems belong to other sonar families. The EM124 was also used on later Five Deeps surveys, but the Puerto Rico Trench mapping in 2018 is the event described here.