Materials:
Secchi disk attached to a calibrated line (usually measured in meters)

Testing Procedure:
1. Place the Secchi disk attached to the calibrated line into the water until it disappears just out of sight.
2. Record the measurement of the line at the surface of the water.
3. Slowly raise the disk until it just reappears into sight.
4. Record the measurement of the line at the surface of the water.
5. Take an average of the two measurements.

Note: If the Secchi disk reaches the bottom before disappearing, the Secchi depth is greater than the water depth and cannot be accurately measured.