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A Sailor's Guide to the San Francisco Bay

From crazy winds to big waves, here is what you need to know about the bad-boy side of San Francisco Bay.

 Sailors beware. The San Francisco Bay is home to some treacherous waters. 

With the first official practice race of the America’s Cup happening in August, San Francisco Bay is about to get a lot more crowded—not only with contestants but also with spectators who want to get a closer look at the action. In fact, news of the race has been increasing traffic on this watery playground for a while now. “We’ve never been so busy,” says Anthony Sandberg, president of OCSC Sailing, a Berkeley-based sailing school and club, who says the boom started right after the announcement that the Bay would be hosting the Cup.

But novices, take note: A combination of feisty winds, speedy currents, and three lanes of big boats coming and going through the infamous Slot, a 1.5-mile stretch passing under the Golden Gate Bridge, makes these waters exciting but also treacherous. If you’re an inexperienced sailor, pay attention to the following quirks.

Winds: San Francisco is famous for its crazy summer winds. Warm air blowing across the Pacific (westerlies) hits the cold waters of the California current just off the coast, while the warm summer inland air rises, allowing the newly cooled air to rush in and replace it. Wind will always take the path of least resistance, and in this case, that path is the Slot.

Big Boats: Three shipping lanes head into San Francisco Bay: the Eastbound lane, which goes between Alcatraz and the city front; the Westbound lane, between Alcatraz and Angel Island; and the Deep Water, a lane that’s almost on top of the Westbound but goes closer to Angel Island. Normally, sailboats have the right-of-way over power boats, but tankers and other enormous boats can’t respond quickly to avoid a potential collision—not to mention the wake they kick up. Bottom line: Whatever the rule, you never, ever want to tangle with a tanker.

Big Waves: Just outside the Golden Gate is a shallow area in the shape of a horseshoe known as the San Francisco Bar, which poses a risk because the waves here tend to be large (the northwest portion, known as the Potato Patch, is the most dangerous).

Tides and eddies: Twice a day, a flood tide rushes in through the Slot and an ebb tide rushes out, creating very powerful—and often sudden—currents that can rattle a boat or throw it off course. And all along the San Francisco waterfront, eddies can actually pull boats in the opposite direction of the main current.

Fog: ’Nuff said.