A Secchi disc being lowered into turbid water
![](https://eatlas.org.au/sites/default/files/styles/m_very_large/public/nesp-twq-5/5-3/MMP%20Secchi%20disc%20photo%20murky%20water%20--%20photo%20by%20Renee%20Gruber.jpg?itok=CC6wqqY-)
Photographers: Renee Gruber
Description
A Secchi disc with alternating black and white quarters is lowered into turbid flood-waters in the Great Barrier Reef Marine Park during February 2019. Secchi discs are a simple and reliable way to measure the depth to which light penetrates the water.