I don't think I'll ever forget that jolt of fear when I first opened my eyes under the water. The thing coming toward me was massive, and I felt naked, exposed, powerless... and just pure terror.

It had taken a lot longer to reach the spot than originally planned--we probably sped along in our motorboat for close to 2 hours before we reached the seemingly innocuous patch of open ocean. This was off the coast of Quintana Roo, near Cancun, Mexico. Finally, we had arrived. And the creature had been spotted. It was time to jump in the water to see what we came for: whale sharks.

Whale sharks are harmless to humans. They're also incredibly alluring in the water, how they seem to glide effortlessly and peacefully through buoyant film. But I was terrified when I first got my bearings and saw the gargantuan fish slowly moving toward me. After a couple of seconds my logical brain took over and I calmly swam alongside the creature for about a minute. It was incredible. Despite moving so "slowly," relative to most things in the ocean, we had to swim near full throttle to keep up with it, as its huge tail fin, the length of my body, powerfully swayed back and forth in the water. Eventually, after kicking furiously after it for several seconds, the guide tapped my foot—it was time to go back to the boat.

The shark seemed totally at ease, indifferent to our presence. Whale sharks inhabit the tropical waters around the equator, and feed on plankton, much like baleen whales. Slow humans nearby are of no concern. And they're probably getting used to us; tourism trips centered around seeing them in their natural habitat are becoming increasingly popular. We just happened to realize it was possible to see them from Cancun while on a family trip. It sure puts our human limitations in the ocean into perspective.

It's amazing that whale sharks even exist on Earth. They are larger than any other fish in the ocean by far (the largest recorded whale shark was 18.8 meters). They have striking, stunning markings on their skin. It's as if God created the world and decided it wasn't interesting enough, and so created whale sharks. And we are the lucky recipients. We enjoy opportunities to not only scale mountains and traverse valleys and explore oceans, but we get to swim with these gentle giants in warm water. What an amazing world we share, with so many other beautiful creatures.