horizontal transparency; water clarity; visibility (diving)
Technical term used in environmental science and diving to describe how far one can see horizontally through water.
The horizontal transparency of this lake is about 10 meters.
I checked the visibility before diving.
Compound of 透視 (tōshi, 'see through') and 度 (do, 'degree'), literally 'degree of seeing through'. The exact historical derivation is uncertain, but the term is a modern technical coinage.