Dolphins, including orcas, are the only marine mammals that make extensive use of echolocation to hunt for prey and navigate their ocean home. Some marine biologists have hypothesized they also emit intense bursts of sound to stun their prey for easier capture. When they are swimming, orcas and other dolphins make low frequency sounds that reflect back to them, helping them understand the topography of the ocean floor and the shoreline, as well as alerting them to the presence of large animals or underwater obstacles. When exploring in more detail or hunting for prey, a series of clicks focused through their melons provides a more vivid three-dimensional picture.