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Tomales Bay's Glowing Waters

On moonless nights, lights of another kind enchant evening kayakers along the California coast.

kayaker on Tomales Bay, Marin County, California, picture
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Photo: Kevin Cooley/Redux
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A kayaker glides through shimmering Tomales Bay.

On moonless nights, starlight illuminates Tomales Bay, a finger of water along the California coast 50 miles north of San Francisco. But lights of another kind also enchant evening kayakers: otherworldly sparkles of blue-green bioluminescence produced by tiny plankton called dinoflagellates.

The flashes are a defense mechanism, says marine biologist Michael Latz of the Scripps Institution of Oceanography. If a predator approaches the dinoflagellates, their light might draw an even larger predator to eat the smaller one. Any disturbance triggers the phenomenon, meaning a hand or paddle stroke can turn the water into a magical paint pot, a passing ray can become a glowing disk, and a speeding fish can leave a glittering streak.

"They're like underwater fireworks," says Dallas Smith, general manager of Blue Waters Kayaking (415-669-2600,, one of several local outfitters that guide groups from spring through fall, when the phosphorescence peaks. The trip is moderately strenuous; in a two-seater kayak a strong paddler can assist a less experienced companion—or one too wonderstruck to paddle.

This article was first published in Summer 2015. Some facts may have aged gracelessly. Please call ahead to verify information.