My nephew and I were swimming in the water a short distance away from our boat when a woman snorkeling not too far away from us suddenly surfaced and shrieked in terror. A whale shark was headed straight towards her, its faint outline gliding under the waves. I smiled knowing that whale sharks pose no threat to humans and feed almost exclusively on plankton. But when I dropped slightly underwater to snorkel and view the spectacle, I realized just how massive this animal is. No wonder that lady was frightened to death.