A thousand years ago, Cnut the Great was a pretty popular guy. He’d not only stopped the Viking hoards from invading England, he eventually became king of the North Sea Empire, which included England, Denmark, Norway and part of Sweden.
He was so successful that, as the legend goes, the flattery from his courtiers was boarding on blasphemous. To prove secular power was no match for the power of God, King Cnut reportedly had his throne set up on the beach and commanded the tide to stop advancing. When it swirled around his feet anyway, he supposedly jumped up and declared, “Let all men know how empty and worthless is the power of kings!”
While probably apocryphal, it’s still a pretty good story. And where we get the phrase “Time and tide wait for no man.”
Today, of course, most people know that the world’s tides and currents are influenced first and foremost by the gravitational pull of the sun and moon. What hasn’t changed since Cnut’s time is that good sailors remain acutely aware of how use tides and currents to their best advantage.
These days, racing sailors are perhaps the most dedicated purveyors of the art. In places like San Francisco Bay, races are as often won by properly playing the currents as properly harnessing the wind. In fact, ‘local knowledge’ is so important that a fast boat in a bad current will often lose to a slow boat in a favorable current.
What kind of currents are we talking about? To answer that, first consider that the only connection San Francisco Bay has to the Pacific Ocean is the one-mile-wide stretch of water under the Golden Gate Bridge. Four times a day, on the ebbs and floods, some 390 billion gallons of water is in motion there. In terms of cubic-meters-per-second, that’s about equal to the outputs of the Congo, Nile and Mississippi rivers combined.
In the spring, when the rain-swollen rivers that feed the Bay are really honking, the ebb under the Golden Gate can run 7 knots or better. It’s enough to literally pull navigational buoys completely underwater.
Farther inside the Bay, currents – and countercurrents - vary quite a bit depending on the time of year, where you are in the cycle, and where you’re sailing.
We’ve heard a lot of great current-related stories over the years. Here are a few of the most memorable ones.
* There are several swimming clubs whose brave members compete regularly in the Bay’s chilly waters. Sometimes they ask the boating community for volunteer ‘mother ships’ – boats assigned to keep tabs on individual swimmers in case they need assistance. One year, a racing sailor volunteered his boat (which powered along next to the swimmer) for a cross-Bay swim. His charge, a middle-aged woman, was in the back third of the pack when she started to head for shore like everyone else. The skipper advised her instead to stay her course a little longer, since she was in a favorable current. She did – and won. The next year, all the swimmers wanted racing sailors on their mother ships.
* “Mother ships” also shadow boats in the annual Bullship Regatta – a race for 8-ft El Toro dinghies across the Golden Gate. The race is always scheduled at “slack water” – in between the ebbs and floods when water under the bridge is still for an hour or so. But sometimes, if the breeze is light, the current will crank up. Even in good breeze, an El Toro’s top speed is maybe 3 knots. So in a full ebb, they can be sailing at top speed toward the finish line, yet still going out the Golden Gate backwards at a knot or two. (At which point they’re rescued by the mother ships.)
The Bullship Regatta heads from Sausalito to San Francisco. Latitude 38
* One of the best windsailing and kitesailing arenas on earth is off Crissy Field, just east of the Golden Gate. But when the boardheads break gear, sometimes it’s hard to get back to the beach. About 10 years ago, a windsurfer broke his mast step and quickly got swept out to sea through the Golden Gate. He reported waving madly to an inbound cruise ship – and the passengers waving gaily back at him, thinking he was just being friendly. He ended up being swept miles down the coast before finally paddling into shore about midnight. (Thank goodness for wetsuits!)
Kiteboard on San Francisco Bay is epic. Photo: Chris Ray
Do you have “current affairs” in your favorite sailing area? Any good stories about them? If so, let us know and we’ll run it/them in a future article here on SummerSailstice.com.
What's the current like in your part of the world? Check out this real-time current display.
