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Balls on a Wire

Oceanographers learn about the temperature, salinity, and movement of water deep below the surface by setting sophisticated instruments on mooring lines that reach from the seafloor to a buoy at or near the surface. Here, a WHOI mooring team deploys a cluster of yellow plastic hardhats attached to a mooring line. Each hardhat encloses a glass ball that provides flotation. If the mooring line breaks, the balls will rise to the surface, carrying the line and instruments with them so they can be retrieved. The WHOI Buoy Group recently celebrated the 50^th anniversary of its first deployment.(Photo by Penny Foster, Woods Hole Oceanographic Institution)