Fish - Fishes have ears, however, they do not have external openings. The ears pick up vibrations and help the fish hear and navigate.Fish also have a unique navigational aid unlike anything found on mammals. The structure is called the lateral line and runs along the side of the fish. The lateral line contains small sensory hairs that can detect even tiny vibrations. This extra organ allows fish to navigate and hunt prey even in low light or cloudy water conditions.