Surfing has come of age. Like rock and roll, it was once strictly for young people, edgy and alternative and physically way too demanding for anyone over the age of 27. But those young people grew up and they’re still at it. For millennials it’s hard to maintain a sense of cool when your parents are heaving their boards into the same breaks and when, according to the marketing people, there are upwards of 35 million surfers worldwide, in a sector that’s worth at least $10 billion per year.