As technology improves, scientists are descending deeper and deeper into the planet's last frontier. Our modern-day explorers are in a race to map and observe the ocean's depths before human appetites and reckless exploitation destroy its undiscovered wonders. Mysteries of the Deep joins a team of scientists, ranging from biologists to volcanologists, on an international expedition to the Mariana Arc, on the Pacific Rim of Fire. Each day they make new discoveries about outlandish deep-sea dwellers and dramatic underwater volcanoes. But even as scientists catalogue these new findings, industrial fisheries are also delving further into deep waters in an attempt to replace diminishing fish stocks along the coasts. Can technology help us understand this little-known world before it's altered forever?