Queen Mary 2 visits San Francisco

The mammoth Queen Mary 2 ocean liner passed under the Golden Gate Bridge on Sunday, clearing the bottom of the span by 27 feet before the vessel began a nail-bitingly tight tour of San Francisco Bay.

The ship was surrounded by scores of sailboats and other water craft as it slid slowly into the bay.

The visit is one of the riskiest passages in modern maritime history -- and a chance for 2,638 passengers to glimpse the underside of the Golden Gate Bridge. It’s also a pit stop for the 1,250-person crew to pick up 150 tons of food.

The hulking QM2 is the largest vessel ever to enter San Francisco Bay, said Cindy Adams, a spokeswoman for Cunard Line. It has traveled 14,145 miles from Fort Lauderdale, Fla., around South America’s Cape Horn. It will continue today to Honolulu, then to the South Pacific, Australia, Asia, Egypt and Europe before returning to Florida on April 2.

The vessel is 134.5 feet wide and 1,131 feet long -- as long as some skyscrapers are tall.

But the dredged-out San Francisco waterfront is so shallow and muddy in places that the ship’s navigational margin for error is less than 70 feet.

San Francisco Bay is home to treacherous currents and tides, which whirl around Alcatraz and churn beneath its iconic, rust-colored bridge. Big container ships enter and exit the bay only during high tide. Some tankers cannot dock there but move upriver on the flood tide to Solano and Contra Costa counties.

Pier 27 juts into the water like a finger, perpendicular to tidal flow.

Docking broadside to a current adds more complexity; a tugboat will be ready in case the ship needs an emergency tow.

Docking the ship is the challenge of a lifetime for Capt. Tom Miller, 49, a San Francisco bar pilot. Such pilots assume navigational control of a ship from the sea entrance to the harbor to the berth.

“It’s a big deal,” said Miller, a graduate of the California Maritime Academy in Vallejo, Calif., who started his career as a tugboat skipper. “This is a big, heavy ship, but she is a good ship and maneuvers well. She has all the latest technology.”