DESCRIZIONE
According to an example aspect of the present invention, there is provided an apparatus (100) for measuring waves travelling a fish cage (102), said apparatus (100) being configured to be attached to the fish cage (102), to receive waves travelling the fish cage (102) and to determine at least one type of waves from the received waves, wherein the apparatus (100) is operatively connected to an alarm system (104) and the apparatus (100) is configured to cause one or more alarm operations of the alarm system (104), when a received wave from the fish cage (102) corresponds to the at least one type of waves.