At first, Half Moon Bay surf instructor Dave Alexander took no notice of the men in khakis spread out on the beach and on a nearby bluff Wednesday.
Then he learned his pupil for the afternoon was Elise Geithner, a Stanford University student and daughter of U.S. Secretary of the Treasury Tim Geithner, and realized the observers were Secret Service members.
While he taught Elise Geithner how to surf, her father and brother, Ben, rode waves nearby, Alexander said.
"It's pretty crazy actually," Alexander said today.
He said he received a call from Geithner on Wednesday morning to set up a surf lesson that afternoon, but he did not realize Geithner was the treasury secretary until Elise told him what her father does for a living.
A representative for Geithner could not be reached.
"They're a very mellow, nice family," Alexander said. "I never would have thought anything other than he seemed like a businessman. It was fun; I had a great time."
Alexander is still not sure how Geithner chose his surf school, Open Ocean Surfing, but he assumes the treasury secretary found him at his website.
The Bay Area native has lived in Half Moon Bay since 1981 and began teaching surf lessons in 1990. He earned a degree in education at the University of California, Santa Cruz and worked as a teacher before opening the surf school.
Alexander said he would have been nervous if he had known ahead of time who his student was, but he was already into the lesson by the time he realized two or three Secret Service members were keeping an eye on the group.
Tim Geithner rode a longboard nearby and was an intermediate/beginner surfer, Alexander said. He said the treasury secretary seemed like an "athletic type" and admitted to playing basketball with President Obama.
"I've never heard of anybody in his position, at that level, being a surfer," Alexander said. "It's kind of cool."
He said the group was on the water between about 1 p.m. and 4 p.m., and that the family and Secret Service members took photos with him after the lesson.
Geithner's trip coincided with a whirlwind Bay Area visit by President Obama.
The president pitched his budget plan Wednesday during an event at Facebook's headquarters in Palo Alto before heading to San Francisco for three fundraisers. He departed San Francisco International Airport Thursday morning.