The passage of time itself is distorted: a couple of long sessions in cold water, hard winds, and big waves can make two days seem like two weeks. Mark has a theory: that the sense-deprivation involved in cold-water surfing can throw the body into a state resembling insulin shock, which causes a similar distortion of time. Mark also has a rule: “For every hour you surf in San Francisco in winter, add one hour of sleep.” The rule has an exception: for Dead Man’s, which has an especially ferocious current, Mark says, “Add two.”
Ocean Beach. The jewel of San Francisco, hiding in plain sight. 

King of Kooks’ Missives to His Subjects: Playing Docs Games: The New Yorker 1992