At the end of our trip to Berkeley last year, we had a bit of time to kill before getting on our plane home. We drove around SF a bit and I really wanted to take the kids to see/hear the Wave Organ in the Marina District. I’d been before, but the seas were flat that day and we didn’t really hear anything. This time, however, there was some small swell coming into the bay and the tubes were working!
See here for pictures of the Wave Organ and a more detailed explanation.