In the hunting phase with ambush technique, for example reaching a grouper, it is more appropriate to move using the free hand and maintaining legs and fins still, avoiding movements of water that could alarm the fish. These, in fact, are equipped with a special sensor, called lateral line, made of receptors (neuromasts) positioned along the side of the fish starting from the back of the gills down to the tail, that perceive with high sensibility the movements of the water.