You know that you are fish obsessed--or just plain loco--if, in the middle of a perfectly good day, you strip down to your boxers, don a snorkel and fins, and plunge into the Pacific Ocean 10 miles offshore where the seafloor is 1,000 feet beneath you. In my case, I was obsessed with the idea of seeing a free-swimming sailfish. And I did. Fifteen minutes into my dip, I spotted a sail 40 feet below me using its eponymous dorsal fin to corral a school of sardines. As the ball of bait tightened, the sail, which was lit up like a neon sign, slashed at the silver mass with its bill, knocking three or four fish silly, and then nonchalantly picked them off as they tumbled downward.