Our earth is covered by more than 75 percent water, yet we know more about the moon than the depths of the sea. Today on World Oceans Day we celebrate and honor oceans by recognizing the underwater footprint we all unknowingly leave behind.

When it comes to plastic, what you throw away doesn't really go away. This was evident on my journey to one of the most remote ends of the earth - the Midway Atoll. This small piece of land in the middle of the Pacific Ocean near the northwestern end of the Hawaiian archipelago was one of the most beautiful places I have ever been to, and should have been the most pristine. There are no cars, streets, lights or air pollution, yet I couldn't escape the remnants of modern society littered everywhere in the form of plastic.

I had heard about this "island of garbage" in 2005 and was immediately intrigued. As a surfer, scuba diver and ocean lover, the ocean has always been an integral part of my life. What started out as research for a short segment for a show I was working on, morphed into an arduous 7-year journey to investigate and unveil the story behind this plastic paradise known as the Great Pacific Garbage Patch.

At the dawn of the 20th century, scientists invented synthetic plastics as a replacement for raw materials. Plastic production grew more than 3,000 percent from 1927-1943. During the height of WWII, 85 percent of that production was devoted to war. This fantastic invention came in all shapes, sizes and materials such as nylon, cellophane, polyester, polystyrene, and methyl methacrylate, which are made to be durable and withstand the elements. There are great uses for plastics but it's the plastic products that are designed to be used once, but are made to last forever, that have become the main problem.

"The biggest landfill it turns out, is our oceans. We are just beginning to realize that," says Lisa Kaas Boyle, an environmental lawyer and co-founder of the Plastic Pollution Coalition.

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"The request is always for a picture of this island of garbage, but there is no such island, the debris is dispersed. We have gotten samples from the Indian Ocean, [and] the Atlantic," says Captain Charles Moore of the Algalita Marine Research Organization who found the garbage patch in 1997 when he accidentally sailed through the area, "There's plastic in all of these oceans."

Because plastics are created from chemicals that are volatile in different environments, they will break down over long periods of time in the oceans through photo degradation, or exposure to the sun. The Scripps Institution of Oceanography at the University of California San Diego has found the proliferation of plastic pieces in our environment has infiltrated our oceans at an alarmingly rapid rate. Its latest study estimates the amount of particles of "microplastic"— pieces of plastic smaller than 5 mm in diameter — has increased more than 100 times since the early 1970s. Last year its team found nearly 10 percent of fish in the area had eaten plastic.

"These ecosystems are very connected. If the oceans are in trouble, we humans are in trouble. We don't realize that we are threatening our own existence," says Dr. Gregor Hodgson, founder and executive director of Reef Check Organization.

Ocean currents move around in a the world in a gyre, which is like a slow-motion whirlpool that opposes the wind and earth's rotational forces. Although the Pacific Ocean is the world's largest body of water, few people realize that there are in fact five subtropical gyres around the world - the North and South Pacific Oceans, North and South Atlantic Oceans, and the Indian Ocean. Dr. Marcus Eriksen, executive director of The 5 Gyres Institute, is currently leading an expedition sailing the course of the Japanese tsunami debris that is headed toward Canada and the U.S. "Having just crossed the western half of the North Pacific, we can report that the ocean is peppered with microplastics from California to Japan," he says.

An estimated 1.5 million tons of Japanese tsunami debris is headed west, and as recently as yesterday, a whole dock from the Japanese fishing town of Misawa arrived on the coast of Oregon. In April a soccer ball washed ashore in the Gulf of Alaska and was recently returned to its owner in Japan.

While filming the documentary, I found myself in serendipitous situations, especially when we encountered a hand-written letter from May 1999. It was written by a third grader in Long Beach, California.

[Related: Watch Angela Sun as she traces where the message in a bottle came from]

At first I thought it would be great to return this to the young man, now probably around 23 years old, who wrote the letter. However, Lisa Dugan, his former teacher, had just thrown away her old records. I realized this message in a bottle found more than 5,000 miles from its origin more than 10 years later carries a much greater message for all of us. This moment was a stark reminder that consumers, producers and legislators should be accountable for what we put into the environment and where our trash ends up.

"The oceans provide our air, [they] provide a lot of our food and [they] regulate our climate," says Greg Stone, senior vice president and chief scientist for oceans with Conservation International. "If you put dollars and cents on those services, then we will be forced to from an economic argument to protect it. Right now we're not aware of those values, but the oceans are actually the most valuable asset we have on this planet—people don't get that."

The message behind the bottle was the tangible evidence of "what goes around comes around."

For more information about the documentary, "Plastic Paradise: The Great Pacific Garbage Patch," and how to get involved, visit www.plasticparadisemovie.com. Follow the journey on Facebook and Twitter.

Angela Sun is a filmmaker, journalist and sportscaster who likes to chase sharks and sunsets. You can find her hosting the Yahoo! Sports Minute daily, on the sidelines of NBC's American Ninja Warrior and anchoring Court Reports on the Tennis Channel. Follow her on Twitter.