Splash! Real-Life Mermaids Seek Beauty of Deep

June 1, 2010 — -- They live in deep waters where light begins to vanish.

As the last remnants of the sun fade into infinity, a whale and her calf rise from the depths. They are the length of submerged airplanes, generating a churning backwash as they move.

Click HERE for a slide show of real-life mermaids.

And there, swimming among them, is what appears to be a legendary figure. In fact, she's very real.

"I'm a mermaid," she says.

That's right: a mermaid.

Her name is Hannah Fraser. She can free dive 50 feet below the sea and return to the surface on a single breath of air. But what's most extraordinary is Hannah's ability to co-exist with animals that can very quickly become unpredictable, even deadly.

Watch the full story tonight on "Superhumans!", a special edition of "20/20" at 10 p.m. ET.

"I have found a way to integrate with their environment and swim with them, and have a level of comfortability that most people will never experience in their life," said Fraser.

It is a feat of great physical daring and athleticism. Unlike most divers, Fraser wears no oxygen tank, no face mask, no warm wetsuit -- only a special mermaid tail.

"The tail gives me so much more propulsion and streamline ability," said Fraser. "I can swim much faster with the tail on than other people can without it. So really fast, strong swimmers can't keep up with me when I'm wearing it. It's like it imbues me with some kind of superhuman powers of confidence and longevity to be in the ocean."

Fraser's fascination began when, at only 3 years old, her stick-figure sketches evolved into painting mermaids. It was only a matter of time before she told her parents that she wanted to become one -- for real.

"I was a complete water baby -- throw me in a pool and I was just on the bottom playing and making up stories about mermaids," Fraser said. "I made my first mermaid's tail when I was 9 years old, and it was definitely not particularly functional. And it's quite amazing that my mother even let me tie my legs together and throw me into the pool with, you know, pillow stuffing down there. It's pretty dangerous."

Fraser has been swimming ever since, with more refined tails. In fact, she's turned her passion into a full-time profession, performing in documentaries, television and aquariums.

It may all seem effortless, but make no mistake -- Fraser's underwater adventures are not for the faint of heart.

"Swimming with the whales was one of the most unbelievable, awe-inspiring experiences that I could ever imagine," Fraser said. "I had this moment where I'm swimming out in the middle of a huge blue ocean, complete depth, cannot see the bottom. Then there's this huge shape that just starts coming up -- it's like the size of a building!

"And I'm like, I don't even know which way to go right now. It's going to come up and I'm going to be on its back and fall into its mouth or its blowhole or something. I can't see. I am powering with all of my might to try to keep up into the same water space as these animals. It is hard work! You have to be really fit to be able to do what I do."