The drone is easily put into the cage. It changes buoyancy by pulling in water and sinks. At the bottom it pushes water out to change buoyancy and floats. On the way up it measures oxygen, temperature, salinity and light. Also the echosounder measures where in the cage the fish are. At the surface it transmits the data and the data then is available online. This way of moving is highly battery efficient and the drone can last about 6 months on a single battery.