noun
horizontal transparency; water clarity; visibility (diving)
Technical term used in environmental science and diving to describe how far one can see horizontally through water.
この湖の透視度は約10メートルです。
The horizontal transparency of this lake is about 10 meters.
ダイビング前に透視度を確認した。
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.