Secchi Depth

Secchi depth is how far down a plain white disk stays visible from the surface: the standard measurement of water clarity, named for the 19th-century disk it's measured with.

Because water clarity is closely tied to chlorophyll concentration, Chlorofishy estimates Secchi depth from satellite chlorophyll data using Secchi depth (m) = 8.69 × chlorophyll (mg/m³)^-0.47. Short reference and formula: Secchi depth and water clarity. Full derivation and validity limits: Estimating Dive Visibility from Satellite Chlorophyll Data.

Check today's estimated visibility on the ocean water clarity map. Back to the glossary.