An improved sensor fish with robust design and enhanced measurement capabilities. This sensor fish contains sensors for acceleration, rotation, magnetic field intensity, pressure, and temperature. A low-power microcontroller collects data from the sensors and stores up to 5 minutes of data on a non-volatile flash memory. A rechargeable battery supplies power to the sensor fish. A recovery system helps locating sensor fish. The package, when ready for use is nearly neutrally buoyant and thus mimics the behavior of an actual fish.