St. Peter and St. Paul Rocks marked the start of the circumnavigation's submerged circuit off Brazil on 24 February. Their appearance where and when predicted gave the navigators a precise check on their work. Triton spent about three and a half hours moving slowly around the rocks for its first trial of periscope photography. Fathometer readings and active sonar helped the crew avoid shallow water while following the bottom topography. The rocks were exposed peaks of the Mid-Atlantic Ridge, so the visible islands gave only a partial indication of the underwater hazards.
Notable Point · 2:06:22-2:09:49
A precise landfall begins Triton's submerged circumnavigation
At the circumnavigation's starting point, Triton's navigators checked their position and used sonar and a fathometer to conduct periscope reconnaissance around underwater peaks.