Bathymetry, the measurement and mapping of ocean depths, has a number of terms used to describe the tools used to conduct such surveys. Some synonyms for the word "bathymeter" include: sonar, acoustic profiler, bathysonde, and depth sounder. Each of these instruments relies on sound waves to measure the distance between the ocean floor and the water's surface. Sonar often refers to the use of underwater sound waves to find and track objects, while acoustic profiler tends to be used to describe a type of sonar that is optimized for bathymetric mapping. Meanwhile, bathysonde and depth sounder are often used interchangeably with bathymeter to describe the same type of device.