A palm-size robot has demonstrated a continuous swim, leap and return to swimming, offering a way to investigate how small underwater machines could cross surface obstacles. The Bhamla Lab describes the platform as combining stacked propellers with a steering rudder. Its September 15 preprint reports a tank demonstration with external power supplied through a tether. [2] [1]
The propeller arrangement gives the robot control over the upward turn needed before a leap. Two propellers sit one above the other, so changing their relative thrust pitches the nose up or down. A tail rudder corrects yaw, the sideways change in heading. These motions have different jobs: pitching points the swimmer toward the surface, while steering keeps its departure aligned. The lab's design brings both controls into the same small platform. [2]
The paper tests the rudder's contribution by comparing water exits with its control switched on and off. Across five trials per condition, departure yaw reached about 3 degrees with control and 22 degrees without it. In a separate tank sequence, the robot cleared an obstacle in all three trials, covering 3.7 body lengths horizontally; the hull itself measures 65 millimetres. The motors stop during the airborne phase, then swimming resumes after re-entry. [1]
An outdoor demonstration extended the test to Boulder Creek, Colorado, using a submerged launch frame and a portable battery connected by the power tether. The authors identify onboard power and repeated hops as future work. That setup matters when judging the application: successfully leaving moving water is one part of crossing a stream repeatedly, and the test does not establish an operating range for a self-contained machine. [1]
For researchers designing aquatic robots, the useful evidence is the controlled change in departure direction and the demonstrated transition back to swimming. The rudder comparison isolates one design choice within this prototype; it does not establish superiority over other robots tested under different conditions. A practical follow-up would track complete crossings and recoveries over many attempts with an onboard battery, including failed departures and landings. That would connect this demonstrated maneuver to the reliability needed for inspection work. [1]