Millions know Jack Johnson as the king of mellowed-out tunes. Fewer know that he grew up surfing Hawaii's most dangerous waves. Or that he donates 100 percent of his touring profits--more than $25 million to date--to environmental nonprofits, including the Waterkeeper Alliance and his Kokua Hawaii Foundation, which promotes environmental education.

When Johnson realized that taking his act on the road is bad for the planet, he considered quitting touring but then decided to donate his tour proceeds instead.

"It does feel good," he says. "My family comes on the road with me. We'll visit a community farm, and I'll tell my kids, 'This is what these shows are all about. We're helping to raise funds for this magical place.'" The singer-songwriter spoke to Sierra about his youth on the water, and about a beatnik book that played an unlikely role in some of his earliest songs.

WHEN I WAS A TEENAGER GROWING UP IN HAWAII, every summer my dad and I would get some friends together and paddle a Hawaiian sailing canoe to an outer island, where we'd camp for a few weeks. There's not much space on those canoes, so everything you'd take would have to fit between you and the person in front of you. An extra pair of dry trunks, a long-sleeve shirt in case there were mosquitoes, maybe a good book or two.

I remember scaling cliffs and jumping into the water, finding underwater caves--it was breathtaking, all the things we did.

One time, some of our crew bailed on us in Hilo, so there were only four of us in a six-man canoe. Sailing back, we had the ama [outrigger] attached to the windward side of the canoe instead of the lee side, so my dad tied a rope on me and sent me out to ride on it so the boat wouldn't flip. I was out there for hours. I remember thinking, "Ah, Dad, what are you doing to me here?" But now that I'm older, it's one of my fondest memories. Every time I'd look over, he'd be just cracking up, looking out at me hugging the ama. 

I came home for the summer after my freshman year of college, and I was pretty homesick. My dad and I decided to put a crew together and paddle from Maui to Molokai. During the trip, I was asking myself, do I want to go back to the mainland or do I want to stay in Hawaii? It was one of those trips that reminded me how much I love Hawaii, but at the same time, I was getting my fill. 

I had a band in college, and we'd just started to write our own songs. So as I was out there in the open ocean on the canoe with my dad, I was writing all these lyrics in my head. Paddling is very rhythmic--you're trying to stay in sync with the rest of the crew--and thinking of lyrics was a good way to pass the time, just saying lines over and over in my head. 

By the time I got to the other side, the good ones stuck with me. I didn't have a notebook, but I did have a copy of Jack Kerouac's On the Road, so I wrote down some of the lines I'd come up with on the book's inside cover and margins. 

I found that book recently, and it was interesting to realize that some of those lyrics made it into songs on my albums. Others I hadn't thought about for a long time.