Corte Madera marathon swimmer Simon Dominguez’s quest to become the first person to swim from the Golden Gate Bridge to the Farallon Islands was thwarted Wednesday by a great white shark just 3-1/2 miles from his rocky goal.

After 18 hours in the cold ocean, the 49-year-old Australian reluctantly but wisely climbed into his support boat when his 16-year-old daughter, Olivia, spotted what was estimated to be a 12- to 15-foot great white circling the boat and swimming toward her father.

As he stood on the deck, blood streamed down his chest from chafed skin around his neck, which may have attracted the shark. “I’m a little bit disappointed,” he said, barely able to speak because of a raw throat from swallowing salt water. “But you can’t control Mother Nature, and she decided to throw a shark at me.”

The Farallones are a breeding ground for great whites, but Dominguez said he decided to make the attempt now before breeding season normally begins in the fall. The 240-pound Aussie jumped into the cold ocean under the Golden Gate Bridge at about 11:15 p.m. Tuesday, wearing only a cap, goggles, swimsuit and a thick coat of grease to guard against jelly fish stings and to keep him a little warmer.

He was beginning what he hoped would be a 14- to 15-hour swim. He aborted it at 5:15 p.m. Wednesday after swimming for more than 25 miles in water in the mid to low 50s. He said he thinks he would have made it if the shark hadn’t forced him to make other plans.

Standing outside at the San Francisco Yacht Club in Belvedere after returning to Marin, he said he would have to check with his wife and daughters before he decides if he’ll try the perilous swim again, one that no swimmer has ever successfully completed.

Asked what his plans for the evening were, he said, “To get drunk.” Then he caught himself, adding, “Make that have a couple of beers.”