Secchi Disk Light Calculator

This tool converts a Secchi disk observation into the depth of specific light fractions (for example 50%, 30%, 5%, 1%) relative to the surface. The calculation uses the classical relationship I = exp(-(h/z) * 1.7), where I is the light fraction, h is depth, and z is the Secchi depth. Provide the Secchi depth, list the target light levels, and optionally add the total water depth to display the seabed on the chart.