Imagine yourself standing on a beach, looking out over the ocean, waves crashing against the shore, blue as far as your eyes can see. Let it really sink in, the sheer scope and size of it all. Now, ask yourself, "How big is it? How big is the ocean?" First thing, we need to understand that there really is only one ocean, consisting of five component basins that we call the Pacific, the Atlantic, the Indian, the Arctic, and the Southern. Each of these five, while generally referred to as oceans in and of themselves, are really and truly a part of a single, massive body of water, one ocean, which defines the very face of planet Earth. The ocean covers roughly 71% of our planet's surface, some 360 million square kilometers, an area in excess of the size of 36 U.S.A.'s. It's such a vast spread, when viewed from space, the ocean is, by far, the dominant feature of our planet. Speaking of space, the ocean currently holds over 1.3 billion, that's billion with a "b", cubic kilometers of water. Put another way, that's enough water to immerse the entire United States under a body of salt water over 132 kilometers tall, a height well beyond the reach of the highest clouds and extending deep into the upper atmosphere. With all that volume, the ocean represents 97% of Earth's total water content. On top of all that, the ocean contains upwards of 99% of the world's biosphere, that is, the spaces and places where life exists. Now let that sink in for a second. The immediate world as we know it, indeed the totality of all the living space encompassed by the continents themselves, all of that represents only 1% of the biosphere. 1%! The ocean is everything else. So, the ocean is physically massive. It's importance to life is practically unparalleled. It also happens to hold the greatest geological features of our planet. Quickly, here are four of the most notable. The ocean contains the world's largest mountain range, the mid-ocean ridge. At roughly 65,000 kilometers long, this underwater range is some 10 times longer than the longest mountain chain found purely on dry land, the Andes. Beneath the Denmark Strait exists the world's largest waterfall. This massive cataract carries roughly 116 times more water per second over its edge than the Congo River's Inga Falls, the largest waterfall by volume on land. The world's tallest mountain is actually found in the ocean, hiding in plain sight. While 4200 meters of Hawaii's Mauna Kea sit above sea level, its sides plummet beneath the waves for another 5800 meters. From its snow-covered top to it's silt-covered bottom, then, this Hawaiian mountain is roughly 10,000 meters in height, dwarfing tiny Everest's paltry peak by well over a kilometer. Then, since we're picking on poor Everest, let's consider the world's deepest canyon, the Challenger Deep, existing 11 kilometers below the ocean's surface, some six times deeper than the Grand Canyon. That's deep enough to sink Mount Everest into and still have over 2.1 kilometers of water sitting atop its newly submerged peak. Put another way, the depth of the Challenger Deep is roughly the same height that commercial airliners travel. So, pretty much however you choose to slice it, the ocean is capital B capital I, capital G, BIG! It defines our planet, home to the greatest geological features, comprises the largest living space, and accordingly, is home to the greatest numbers and forms of life on Earth. It is practically incomprehensible in scope. But it is not so big, so vast, so extraordinary as to be untouchable. In fact, with roughly 50% of the world's population living within 100 kilometers of the coastline and with most of the remainder living close enough to lakes, rivers, or swamps, all of which ultimately lead to the ocean, virtually every single person on the planet has the opportunity to influence the general health and nature of the world ocean. Evidence of human influence is seen in every part of the ocean, no matter how deep, no matter how distant. The ocean defines our planet, but, in a very real sense, we define the ocean.