Hearing is an important sense underwater, as it allows for prey detection, predator avoidance, and long-distance communication. The growing presence of anthropogenic noise in our oceans poses a threat to the physiology and behaviors of marine animals. However, to understand how this threat may affect marine animals, their hearing structures need to be investigated. Increasingly, researchers have been exploring the sound reception structures of marine invertebrates. The crustacean statocyst has been studied for over 150 years. It is a mechanosensory structure used primarily for maintaining equilibrium and is found in most crustacean taxa. While its form, shape, and location vary with taxa, the overall structure remains conserved. More recent work has shown how some species use the statocyst for sound detection. Here, the authors describe the function of the statocyst, the morphological diversity of statocysts found in crustaceans, and the function of the statocyst as a sound detection structure. Opportunities to broaden our understanding of the statocyst and potential future directions for research are identified.