Estimating Dive and Water Visibility

Chlorofishy estimates underwater visibility (Secchi depth) from chlorophyll concentration using Z = 8.69 × chl^-0.47, and shows it as a click readout on the chlorophyll layer. Here's where to find it and what it does and doesn't tell you.

Where do I see a visibility estimate?

Click or tap anywhere on the chlorophyll layer. Alongside the mg/m³ reading, the popup shows an estimated visibility in both feet and meters, labeled "Offshore estimate only." It uses the same click-to-read popup as every other data point on the map. See reading the map for how that readout works.

How is the estimate calculated?

Visibility in meters is 8.69 times chlorophyll concentration (mg/m³) raised to the power −0.47, a standard empirical relationship between phytoplankton concentration and water clarity. Because the relationship runs backwards (more chlorophyll means less visibility), the same conversion is used when you set an alert condition in visibility units instead of mg/m³. See alert conditions and logic.

What are the limits of this estimate?

This is an offshore, open-water estimate derived purely from chlorophyll: it doesn't account for sediment, runoff, or nearshore turbidity, so it's most reliable well off the coast and least reliable close to shore or after heavy rain. For the full science behind the formula and where it holds up, see the longer article on Secchi depth and water visibility, or how to use Chlorofishy for everything else on the map.