The present invention relates to a method and apparatus for collecting and/or pre-processing data related to feeding animals in water. More particularly, the present invention relates to a method and apparatus for minimising wasted feed used in a fish farm. According to an aspect, there is a provided a computer-implemented method for detecting motion in relation to one or more aquatic animals, the method comprising the steps of: receiving sensor data; determining from the sensor data one or more moving objects using one or more learned functions; and generating output data in relation to the determined one or more moving objects.