Underwater vision method for low-visibility turbulent conditions

During rescue work after a ´bus fell from the Hintze Ribeiro bridge into the Douro river in Portugal on 4 March 2001, a device was invented which can visualize underwater objects whose rough location is obtained by standard acoustic sonar. A canvas flexible diving bubble having a transparent window was filled with clean water. An underwater camera and light within the bubble transmit video to the surface through an electric cable. The whole set is maneuvered with the help of ropes and a rudder. A weight is used to overcome forces causing the device to dive. In strong currents, a rudder is useful for orientation. Visibility is near zero. When the diving bubble touches an object, the camera transmits the contact image profile, which is often good enough to identify objects. Holes can be remotely located and used to fix hooks. The principle can also be applied in polluted sea waters. Any nontransparent fluid can be inspected to locate leaks, provided that the viscosity is not high enough to prevent an optical path between the clean water medium and the immersed object when approached by the bubble