Institute for Physical AI @ JBI · a demonstration

What holds it at depth?

A robotic fish, taken apart three ways: the body that swims, the one rule of moving through water, and the brain that sets its pace. This is the body, drag to turn it over, then take it apart. It has no rotor and no legs, yet it holds its depth for almost nothing; the reason is the water itself. The source on the right runs the real swimming physics, so it cannot lie to you.

Provenance. A body submerged in water feels an upward buoyant force equal to the weight of the water it displaces (Archimedes): ρ·V·g. Tuned to neutral buoyancy, the robot displaces exactly its own weight in water: that force cancels gravity, so the net vertical force is zero and holding depth costs no power at all. The water does what a drone's rotor must do continuously. What moving through the water costs is the next lesson. All numbers computed live by the Institute's open swim core. The 3D model is illustrative; the numbers are exact.