A soft robot for agile and efficient marine locomotion

Exploring underwater environments such as coral reefs and shipwrecks without disturbing fragile ecosystems requires a new class of underwater robots. Conventional autonomous and remotely operated vehicles are optimized for open-water operation and struggle in complex spaces. Biomimetic soft robots offer compliance and environmental compatibility but typically sacrifice speed, efficiency, or controllability. We present DRAGON 3D (Deformable Robot for Agile Guided Observation and Navigation in Three-Dimensions), a flexible vectored underwater vehicle that integrates a single thruster with a cable-actuated deformable body for three-dimensional maneuverability. A dynamic model and simulation were developed to guide motion planning and were validated through three experimental trajectories. DRAGON 3D was tested in both controlled and natural environments, including a pool, a shallow riverbed, and a coastal pier. It was tested with an acoustic communication system to demonstrate the potential for tetherless operation. The robot executed teleoperated maneuvers including slalom, targeted depth changes, and traversal of confined spaces within a cave and a mock shipwreck. It also captured video of marine organisms and collected environmental sensor data in freshwater and marine settings. These results demonstrate that DRAGON 3D achieves a balance between compliance and controllability, providing a practical platform for minimally invasive underwater exploration, monitoring, and ecological research.