  Underwater cameras are widely used to observe the sea floor. They are usually
included in autonomous underwater vehicles, unmanned underwater vehicles, and
in situ ocean sensor networks. Despite being an important sensor for monitoring
underwater scenes, there exist many issues with recent underwater camera
sensors. Because of lights transportation characteristics in water and the
biological activity at the sea floor, the acquired underwater images often
suffer from scatters and large amounts of noise. Over the last five years, many
methods have been proposed to overcome traditional underwater imaging problems.
This paper aims to review the state-of-the-art techniques in underwater image
processing by highlighting the contributions and challenges presented in over
40 papers. We present an overview of various underwater image processing
approaches, such as underwater image descattering, underwater image color
restoration, and underwater image quality assessments. Finally, we summarize
the future trends and challenges in designing and processing underwater imaging
sensors.
