  Soft underwater robots typically explore bioinspired designs at the expense
of power efficiency when compared to traditional underwater robots, which
limits their practical use in real-world applications. We leverage a fluidic
closed-loop controller to actuate a passive underwater glider. A soft
hydrostatic pressure sensor is configured as a bangbang controller actuating a
swim bladder made from silicone balloons. Our underwater glider oscillates
between the water surface and 4 m depth while traveling 15 m translational. The
fluidic underwater glider demonstrates a power efficiency of 28 mW/m. This work
demonstrates a low-cost and power-efficient underwater glider and
non-electronic controller. Due to its simple design, low cost, and ease of
fabrication using FDM printing and soft lithography, it serves as a starting
point for the exploration of non-electronic underwater soft robots.
