By combined photographic and photovoltaic photometry, the transmission of the light from an argon-ion laser beam through aerated tap water was studied in an approximately coaxial active optical system. The transmittance of the aerated water in the tank was varied from 0.0027 to 0.52%. The approximate range of detectability through the water tank and return for a target having a diffuse reflectivity of 11.5% was 6.1 attenuation lengths (tank transmittance = 0.22%). The signal and backscatter intensity were then both about 10-1° watt/cm2, the signal power about 2 x 10-12 watt and the integrated exposure energy from the signal about 0.06 erg/cm2. A range of at least 7 attenuation lengths is predicted, if a crossed polarizer is used at the receiver. The limiting range of detection of a specular reflection of about 0.3% off the interface between the water and plastic exit window was 10 attenuation lengths. The calculated signal was then about 10-12 watt, the light intensity about 10-10 watt/cm2, and integrated film exposure about 0.1 erg/cm2.
"Limiting Range of Detection through Water In a Nearly Coaxial Optical Transmitter-Receiver System," Optical Engineering 16(2), 162167 (1 April 1977). https://doi.org/10.1117/12.7972094