Excerpt
1. Welcome to Planet Ocean
If you’ve ever looked at a globe or a map of Earth, you might notice something right away: there's a lot of blue. Oceans, seas, lakes, rivers—it’s all over the place. But just how much of our planet is actually covered in water? Get ready for a number that might surprise you: around 71 percent of Earth’s surface is water. That means if you divided Earth into four big puzzle pieces, almost three of them would be ocean or water of some kind. Only one piece would be land.
It’s kind of wild to think about. You walk on land every day. You sleep on land, eat on land, build cities and schools and roller coasters on land. But that land? It’s just a skinny layer compared to all the water out there. Earth might feel like it’s mostly dirt and rock, but it’s really a giant water world.
Let’s shrink Earth down to the size of an apple. The skin of the apple would be the land—thin and fragile. Everything else? That’s where water takes over. If aliens flew by and peeked at our planet from space, they'd probably nickname it something like "The Blue Planet." It’s not just a pretty nickname either. The oceans stretch across huge distances—Pacific, Atlantic, Indian, Arctic, and Southern. And they’re all connected, like a watery superhighway.
But even though there's a lot of water, not all of it is the same. And here's the part that trips people up: most of that water is saltwater. In fact, almost 97 percent of Earth's water is salty, swirling around in the oceans. Only about 3 percent is fresh water—the kind we can drink or use for farming and washing. And even that tiny slice is mostly locked away in glaciers, snow, or deep underground. Less than 1 percent is easy to get to, like in rivers and lakes. That’s the water that helps us grow food, take showers, and fill up swimming pools.
Think about it this way: if all the water on Earth were put into one giant bucket, almost the whole bucket would be ocean. Just a tiny spoonful would be fresh water we could actually use.
But back to the big picture. Let’s talk size. The Pacific Ocean alone is bigger than all the continents put together. It’s so wide that if you stood on a beach in California and pointed across the ocean, you’d be pointing at Japan or Australia—thousands of miles away. And underneath all that water are underwater mountains, canyons deeper than the Grand Canyon, and entire ridges that stretch across the globe like giant wrinkles on the sea floor.
Even the deepest part of the ocean—called the Mariana Trench—goes down nearly seven miles. That’s deeper than Mount Everest is tall. If you could drop the tallest mountain on Earth into the Mariana Trench, its tip would still be underwater. That’s how massive and mysterious the oceans are.
Now here’s something to think about: even though water covers most of Earth’s surface, it’s actually a very thin layer if you compare it to the whole size of the planet. Earth’s radius is about 4,000 miles. But the deepest ocean? Only about 7 miles deep. It's like spreading a coat of paint over a basketball. Thin, but powerful.
And it’s not just the oceans doing the work. Water is always on the move. It travels as clouds in the sky, flows in rivers, hides in soil, and freezes into ice. It’s constantly cycling—falling as rain, running off mountains, soaking into the ground, or drifting back into the air as vapor. This giant system helps keep everything alive—from tiny bugs to giant whales. Without water, there’d be no forests, no people, no pizza. Nothing.
You might be wondering how all this water got here in the first place. Some scientists think Earth’s water came from ancient volcanoes that released steam, which turned into clouds and rained down for thousands of years. Others think water arrived on comets—icy space rocks—that crashed into Earth long ago. However it happened, we ended up with oceans that stretch as far as the eye can see.
But here's something fun to consider: we’ve explored way more of space than we have of our own oceans. Even today, more than 80 percent of the ocean is still unmapped and unexplored. That’s right—we know more about the surface of Mars than we do about the bottom of the sea. There could be giant squids, glowing jellyfish, or even new species we haven’t met yet, swimming around in the deep.
Water doesn’t just cover most of Earth—it shapes it. The coastlines, beaches, islands, and cliffs you see? All formed and carved over time by the motion of water. Waves crash against the shore, rivers wear away rock, glaciers slide across land like slow, icy bulldozers. Even deserts were once shaped by water that’s long gone.
Water connects everything. It links continents, carries heat around the globe, and creates weather patterns like hurricanes and monsoons. When scientists study climate and weather, they don’t just look at clouds—they look at oceans. Ocean water stores heat from the sun and slowly releases it. This helps balance Earth’s temperature, kind of like a giant thermostat.
Why oceans matter to everyone
If you’re miles from the coast, with no sandy beach or seagulls in sight, the ocean might feel like something that only matters to people who live in beach towns or go on cruises. But here’s the truth: oceans are busy doing work for you every single day, no matter where you live. Even if you’re deep in the middle of a city or way out in a desert, the ocean is still part of your life.
Let’s start with the air you’re breathing right now. Take a deep breath. About half of the oxygen in that breath came from the ocean. Not from trees, not from houseplants—from tiny ocean plants floating near the surface of the sea. These little guys are called phytoplankton, and even though they’re way too small to see without a microscope, they work like tiny factories, turning sunlight into oxygen. They do this all day, every day, quietly helping keep every human and animal on Earth alive.
Now think about the weather outside. Is it sunny? Raining? Cold? Warm? The ocean had a say in that, too. It holds onto heat from the sun and slowly releases it, like a giant heat pack wrapped around the planet. That heat moves through the air and creates winds, clouds, and storms. A lot of the rain and snow that falls on land starts with water that came from the ocean, traveled through the sky, and returned in a totally different place. If you’ve ever splashed in a puddle or watched a thunderstorm roll in, you’ve experienced part of the ocean’s power—even if you’re nowhere near the coast.
The food you eat might be connected to the ocean, too. Some of it literally comes from the sea—like fish, shrimp, seaweed, or salt. But even food that grows on land depends on rain and temperature, which are shaped by ocean currents. Farmers need the right weather to grow crops. If the ocean stopped helping regulate the climate, a lot of plants and animals wouldn’t survive. That includes crops like rice, corn, and wheat—foods that people all over the world rely on.
Even something like chocolate needs the right balance of rain and sun, and that balance comes from Earth’s water cycle. And the water cycle only works because of the ocean.
And here’s something else that might surprise you: the ocean plays a huge role in protecting Earth from getting too hot. All around the world, people are burning fuels like coal and gas, which release carbon dioxide (CO₂) into the atmosphere. That CO₂ traps heat, which can lead to changes in climate. But the ocean? It’s like a giant sponge. It absorbs a lot of that carbon dioxide and heat, slowing down the effects of climate change.
It’s not a perfect fix, and the ocean can only do so much before it gets overwhelmed—but for now, it’s still working hard to keep Earth from overheating. Without that backup, we’d be in big trouble.
Let’s talk transportation. Ever looked at a tag on your clothes or a sticker on your toys and noticed it says “Made in” a different country? Maybe China, India, Mexico, or Indonesia? Most of those things didn’t fly to your store—they floated. Huge ships called cargo vessels carry products across the ocean every day. Your backpack, your cereal bowl, even the parts of your tablet or game console may have crossed an ocean before they reached your hands.
Even energy is connected to the sea. In some places, the movement of ocean tides helps power homes and buildings. There’s also oil and gas beneath the ocean floor, though it’s tricky to get and not great for the environment. More scientists are working on clean ocean energy, like using waves and wind to power cities without pollution. If they succeed, we might one day plug in our devices with energy coming straight from the sea.
Let’s get a little closer to the coast—even if just in our minds. Coral reefs, for example, are found in warm, shallow parts of the ocean, and they’re sometimes called “rainforests of the sea.” They’re packed with life—colorful fish, sea turtles, anemones, crabs, and more. These reefs help protect coastlines from big waves and storms. They also support millions of people who rely on fishing and tourism to make a living.
But coral reefs are in danger because the ocean is getting warmer and more polluted. When reefs die, not only do animals lose their homes, but communities that depend on them lose food, jobs, and protection from storms. This kind of trouble doesn’t just stay in one place—it ripples out.
Here’s the thing: when you throw something away, it might not stay where you left it. Plastic bags, straws, bottle caps, and wrappers often end up in rivers, which lead to the ocean. That trash doesn’t vanish. It floats, sinks, or breaks into tiny pieces called microplastics, which can be eaten by fish and other animals. And those fish might end up back on someone’s dinner plate.
Even if you’re super far from the sea, your actions can still affect it. But that also means you have the power to help it. What you do matters. Whether it’s using less plastic, turning off lights to save energy, or learning more about how the ocean works, every choice adds up.
Water also connects people. Countries that might seem really different are joined by the same oceans. Think about that: people living in different time zones, speaking different languages, all sharing the same sea. That’s part of what makes Earth special—it’s one giant, connected system.
If you’ve ever looked at a globe or a map of Earth, you might notice something right away: there's a lot of blue. Oceans, seas, lakes, rivers—it’s all over the place. But just how much of our planet is actually covered in water? Get ready for a number that might surprise you: around 71 percent of Earth’s surface is water. That means if you divided Earth into four big puzzle pieces, almost three of them would be ocean or water of some kind. Only one piece would be land.
It’s kind of wild to think about. You walk on land every day. You sleep on land, eat on land, build cities and schools and roller coasters on land. But that land? It’s just a skinny layer compared to all the water out there. Earth might feel like it’s mostly dirt and rock, but it’s really a giant water world.
Let’s shrink Earth down to the size of an apple. The skin of the apple would be the land—thin and fragile. Everything else? That’s where water takes over. If aliens flew by and peeked at our planet from space, they'd probably nickname it something like "The Blue Planet." It’s not just a pretty nickname either. The oceans stretch across huge distances—Pacific, Atlantic, Indian, Arctic, and Southern. And they’re all connected, like a watery superhighway.
But even though there's a lot of water, not all of it is the same. And here's the part that trips people up: most of that water is saltwater. In fact, almost 97 percent of Earth's water is salty, swirling around in the oceans. Only about 3 percent is fresh water—the kind we can drink or use for farming and washing. And even that tiny slice is mostly locked away in glaciers, snow, or deep underground. Less than 1 percent is easy to get to, like in rivers and lakes. That’s the water that helps us grow food, take showers, and fill up swimming pools.
Think about it this way: if all the water on Earth were put into one giant bucket, almost the whole bucket would be ocean. Just a tiny spoonful would be fresh water we could actually use.
But back to the big picture. Let’s talk size. The Pacific Ocean alone is bigger than all the continents put together. It’s so wide that if you stood on a beach in California and pointed across the ocean, you’d be pointing at Japan or Australia—thousands of miles away. And underneath all that water are underwater mountains, canyons deeper than the Grand Canyon, and entire ridges that stretch across the globe like giant wrinkles on the sea floor.
Even the deepest part of the ocean—called the Mariana Trench—goes down nearly seven miles. That’s deeper than Mount Everest is tall. If you could drop the tallest mountain on Earth into the Mariana Trench, its tip would still be underwater. That’s how massive and mysterious the oceans are.
Now here’s something to think about: even though water covers most of Earth’s surface, it’s actually a very thin layer if you compare it to the whole size of the planet. Earth’s radius is about 4,000 miles. But the deepest ocean? Only about 7 miles deep. It's like spreading a coat of paint over a basketball. Thin, but powerful.
And it’s not just the oceans doing the work. Water is always on the move. It travels as clouds in the sky, flows in rivers, hides in soil, and freezes into ice. It’s constantly cycling—falling as rain, running off mountains, soaking into the ground, or drifting back into the air as vapor. This giant system helps keep everything alive—from tiny bugs to giant whales. Without water, there’d be no forests, no people, no pizza. Nothing.
You might be wondering how all this water got here in the first place. Some scientists think Earth’s water came from ancient volcanoes that released steam, which turned into clouds and rained down for thousands of years. Others think water arrived on comets—icy space rocks—that crashed into Earth long ago. However it happened, we ended up with oceans that stretch as far as the eye can see.
But here's something fun to consider: we’ve explored way more of space than we have of our own oceans. Even today, more than 80 percent of the ocean is still unmapped and unexplored. That’s right—we know more about the surface of Mars than we do about the bottom of the sea. There could be giant squids, glowing jellyfish, or even new species we haven’t met yet, swimming around in the deep.
Water doesn’t just cover most of Earth—it shapes it. The coastlines, beaches, islands, and cliffs you see? All formed and carved over time by the motion of water. Waves crash against the shore, rivers wear away rock, glaciers slide across land like slow, icy bulldozers. Even deserts were once shaped by water that’s long gone.
Water connects everything. It links continents, carries heat around the globe, and creates weather patterns like hurricanes and monsoons. When scientists study climate and weather, they don’t just look at clouds—they look at oceans. Ocean water stores heat from the sun and slowly releases it. This helps balance Earth’s temperature, kind of like a giant thermostat.
Why oceans matter to everyone
If you’re miles from the coast, with no sandy beach or seagulls in sight, the ocean might feel like something that only matters to people who live in beach towns or go on cruises. But here’s the truth: oceans are busy doing work for you every single day, no matter where you live. Even if you’re deep in the middle of a city or way out in a desert, the ocean is still part of your life.
Let’s start with the air you’re breathing right now. Take a deep breath. About half of the oxygen in that breath came from the ocean. Not from trees, not from houseplants—from tiny ocean plants floating near the surface of the sea. These little guys are called phytoplankton, and even though they’re way too small to see without a microscope, they work like tiny factories, turning sunlight into oxygen. They do this all day, every day, quietly helping keep every human and animal on Earth alive.
Now think about the weather outside. Is it sunny? Raining? Cold? Warm? The ocean had a say in that, too. It holds onto heat from the sun and slowly releases it, like a giant heat pack wrapped around the planet. That heat moves through the air and creates winds, clouds, and storms. A lot of the rain and snow that falls on land starts with water that came from the ocean, traveled through the sky, and returned in a totally different place. If you’ve ever splashed in a puddle or watched a thunderstorm roll in, you’ve experienced part of the ocean’s power—even if you’re nowhere near the coast.
The food you eat might be connected to the ocean, too. Some of it literally comes from the sea—like fish, shrimp, seaweed, or salt. But even food that grows on land depends on rain and temperature, which are shaped by ocean currents. Farmers need the right weather to grow crops. If the ocean stopped helping regulate the climate, a lot of plants and animals wouldn’t survive. That includes crops like rice, corn, and wheat—foods that people all over the world rely on.
Even something like chocolate needs the right balance of rain and sun, and that balance comes from Earth’s water cycle. And the water cycle only works because of the ocean.
And here’s something else that might surprise you: the ocean plays a huge role in protecting Earth from getting too hot. All around the world, people are burning fuels like coal and gas, which release carbon dioxide (CO₂) into the atmosphere. That CO₂ traps heat, which can lead to changes in climate. But the ocean? It’s like a giant sponge. It absorbs a lot of that carbon dioxide and heat, slowing down the effects of climate change.
It’s not a perfect fix, and the ocean can only do so much before it gets overwhelmed—but for now, it’s still working hard to keep Earth from overheating. Without that backup, we’d be in big trouble.
Let’s talk transportation. Ever looked at a tag on your clothes or a sticker on your toys and noticed it says “Made in” a different country? Maybe China, India, Mexico, or Indonesia? Most of those things didn’t fly to your store—they floated. Huge ships called cargo vessels carry products across the ocean every day. Your backpack, your cereal bowl, even the parts of your tablet or game console may have crossed an ocean before they reached your hands.
Even energy is connected to the sea. In some places, the movement of ocean tides helps power homes and buildings. There’s also oil and gas beneath the ocean floor, though it’s tricky to get and not great for the environment. More scientists are working on clean ocean energy, like using waves and wind to power cities without pollution. If they succeed, we might one day plug in our devices with energy coming straight from the sea.
Let’s get a little closer to the coast—even if just in our minds. Coral reefs, for example, are found in warm, shallow parts of the ocean, and they’re sometimes called “rainforests of the sea.” They’re packed with life—colorful fish, sea turtles, anemones, crabs, and more. These reefs help protect coastlines from big waves and storms. They also support millions of people who rely on fishing and tourism to make a living.
But coral reefs are in danger because the ocean is getting warmer and more polluted. When reefs die, not only do animals lose their homes, but communities that depend on them lose food, jobs, and protection from storms. This kind of trouble doesn’t just stay in one place—it ripples out.
Here’s the thing: when you throw something away, it might not stay where you left it. Plastic bags, straws, bottle caps, and wrappers often end up in rivers, which lead to the ocean. That trash doesn’t vanish. It floats, sinks, or breaks into tiny pieces called microplastics, which can be eaten by fish and other animals. And those fish might end up back on someone’s dinner plate.
Even if you’re super far from the sea, your actions can still affect it. But that also means you have the power to help it. What you do matters. Whether it’s using less plastic, turning off lights to save energy, or learning more about how the ocean works, every choice adds up.
Water also connects people. Countries that might seem really different are joined by the same oceans. Think about that: people living in different time zones, speaking different languages, all sharing the same sea. That’s part of what makes Earth special—it’s one giant, connected system.