Abstract
Almost nothing is visible in water because of the large attenuation of light. This paper presents the brief history of underwater acoustics and the latest acoustic technology for underwater visualization. Aristotle(384-322 B.C.) has recognized that sound could be heard in water as well as air. Leonardo da Vinci(1452-1519) observed that one could hear ships from afar. Paul Langevin(1872-1946) detected a submarine for the first time, in 1918, as deep as 1500 meters with his piezoelectric transducer.
Underwater detection systems were developed for the purpose of underwater navigation by submarines in World War I and in particular after the Titanic sank in 1912. Many types of SONAR(SOund NAvigation and Ranging) were developed, Echo sounder, Side scan sonar, Multi-beam echo sounder(MBES), Scanning sonar.
Today new acoustic equipments produce the 3D image of seabed, and the underwater movie.
