2. Underwater optical propagation

Seawater is both an absorbing and scattering medium. Absorption and scattering are largely due to the presence of organic or mineral particles, generally larger than the wavelength, suspended in seawater. Particle density can vary enormously from one type of water to another, but whatever the density, seawater always presents a spectral window of least attenuation located in the blue-green (figure 3 ) between 410 nm and 550 nm. The absorption minimum changes with the particulate load of the water under consideration, shifting slightly towards yellow as the particulate load increases.