Figure 3. Depth-holding ability of the 16 M-AUEs for the 5-hour at-sea experiment.

Once at depth, the M-AUEs maintained their target of 10 m with an s.e. of ± 1.02 m using small motions of the piston to counteract vertical currents and density changes caused by internal waves. Black lines show depths of individual M-AUEs. Red vertical lines show the times of panels a–f in figure 5, and gray shaded area shows the time period of panels g and h in figure 5.