Secchi Disk, 1 Each

The United Scientific® Secchi Disk measures water clarity with a 7.7 in white plastic disk printed with permanent black sectors. It comes with an attached sinker and approximately 72 ft (22 m) of rot-proof polymer line marked at every foot, stored on a foam bobbin, so depth can be read straight from the line. Environmental science and biology teachers use it for pond, lake and stream water-quality monitoring.