A few minutes later, Stan saw something else he wanted to show me and headed back down, holding my hand. When we were about five feet away, he wouldn't let me get any closer and pointed to a particular hole in the coral. Finally, I saw a speckled brown head sticking about four inches out of the hole and recognized it as an eel. We watched each other awhile, neither of us eager to get closer to the other, then Stan headed for the surface again. He took his snorkel out of his mouth when we reached the surface so he could speak.

"You can stay down a fairly long...