Definitions for "Secchi Disk"
A device used to measure the depth of light penetration in water.
A white disk 12" or more in diameter which is lowered into the sea to estimate transparency of the water. The depths are noted at which it first disappears when lowered and reappears when raised.
a black and white patterned disk used to measure the clarity of water in visibility distance.
Keywords:  see
see secchi.