A Deep Sea World Beyond Your Imagination

How deep is the ocean? Did you know that 70% of the Earth's surface is covered by oceans? And 96% of all the water on Earth is seawater. In essence, our planet is truly an oceanic planet. Yet, humanity knows very little about the oceans. It's said that we've explored less than 5% of them. That's about the same proportion as our understanding of the universe. Today, let's dive into the mysteries of the ocean together. Do you know the average depth of the ocean? It's 3680 meters. In comparison, the average elevation of the Earth's land is only 860 meters. This shows just how deep and vast the oceans are. The deepest part of the ocean? That would be the Mariana Trench, which plunges over 11,000 meters deep. That's far taller than Mount Everest. In fact, the distance from the peak of Mount Everest to the deepest part of the Mariana Trench is over 20,000 meters. Now, let's officially begin our descent. At 3 meters deep, we're at the typical depth for casual swimming. Let's go further to 20 to 30 meters. At this depth, we find vibrant coral reefs and aquatic plants. Descending to 40 meters, we hit the limit of recreational diving. Beyond this depth, divers can start experiencing joint pain, dizziness, and symptoms similar to altitude sickness. Interestingly, it seems like nature discourages us from going too far up or down. The world's deepest swimming pool? It's also 40 meters deep, located in an Italian hotel called Monte Grado Term. This pool is designed specifically for diving enthusiasts. At 70 meters, things start to get strange. Humans may experience hallucinations. This is also the habitat of the largest fish species, the whale shark. At 100 meters, we reach the limit of professional diving. Here lives the giant Pacific octopus, which can change colors like a chameleon. This massive creature can grow up to 6 meters long, often being mistaken for a sea monster. At 130 meters, we find the deepest underwater wedding ever held. In 2014, a Japanese and an American diver tied the knot in Thailand at this depth. Even their officiant, a priest who doubled as their diving instructor, joined them underwater. At 200 meters, we officially enter the deep sea, where light is no longer sufficient for photosynthesis. This means no green plants can grow here. However, you might encounter creatures like the oarfish, also known as the king of herrings, a long, ribbon-like fish. This is also where an extreme sport called freediving comes into play. Freedivers hold their breath and dive as deep, as far, or for as long as possible. The world record for freediving is held by an Austrian named Herbert Nitsch, who descended to 214 meters in 2007 on a single breath. Surviving such depths is nearly impossible for most people due to the immense pressure, which can crush organs and cause permanent damage. Nitsch managed it by using pressure to compress his abdomen, pushing his internal organs upward to protect his lungs. When it comes to breath holding, the world record for static apnea, holding your breath while still, is an astonishing 22 minutes and 22 seconds achieved by Danish diver Stig Severinsen. However, he used pure oxygen beforehand. At 300 meters, we meet the giant spider crab, with legs stretching up to 4 meters. Humans have also reached these depths with the recorded dive using such equipment is 332 meters. Ready to go even deeper? Stay tuned for what lies further below. The world record for the deepest scuba dive belongs to an Egyptian diver named Ahmed Ghabr. In 2014, Ghabr descended to an astonishing depth of 332 meters using an oxygen tank. Initially, his goal was to reach 350 meters, but at 332 meters, he lost sensation and started experiencing intense hallucinations. Realizing the risk, he had no choice but to begin his ascent. It took him only 15 minutes to descend to this depth, but resurfacing required an incredible 13.5 hours, making the total dive time 14 hours. Why did the ascent take so long? The air in his tank was a mix of oxygen, nitrogen, and other gases. At such extreme depths, the pressure forces these gases into the bloodstream as tiny bubbles. If a diver ascends too quickly, the bubbles rapidly expand, potentially causing the blood vessels to rupture, a condition known as decompression sickness or the bends. In severe cases, this can lead to oxygen toxicity, causing permanent damage to the eyes, spinal cord, or central nervous system. To avoid this, Ghabr ascended at a controlled pace of just 25 meters per hour, allowing the gases to gradually escape through his lungs. His ascent was meticulously monitored by a team of 30 staff members, ensuring his safety. This record remains unchallenged to this day. For comparison, most submarines operate at depths between 300 and 500 meters. Let's continue our descent to 500 meters, where we leave the human realm and enter the world of marine animals. At this depth, we find the mighty blue whale, the largest animal on Earth. Blue whales are not just massive in size, they also have incredibly powerful voices. Their calls can reach 188 decibels, louder than a jet engine, and travel up to 1,600 kilometers through the water. With a single call, they can summon pods of whales from vast distances. Surprisingly, emperor penguins, the largest species of penguin, can also dive to this depth. These remarkable birds can stay underwater for up to 10 minutes, making them the most pressure-resistant birds in the world. To put this depth into perspective, 500 meters is roughly equivalent to the height of Taipei 101. At 600 meters, we encounter the barreleye fish, a bizarre species with a transparent head. Its eyes are located inside its head and point upward, allowing it to spot prey above. This fish is almost impossible to capture. When brought to the surface, it explodes due to the change in pressure. This depth is comparable to the height of Tokyo Skytree. Descending further to 700 meters, we find the European eel. While commonly associated with rivers, these eels spend half their lives in the ocean and only return to rivers to spawn, where they often become a delicacy for humans. At 900 meters, we reach the habitat of the giant squid. These creatures can grow up to 10 meters long, with eyes as large as a human head. Although rarely seen, scientists believe giant squids are relatively abundant, but their elusive nature keeps them hidden in the deep. At 1,000 meters, we enter the mesopelagic zone, where no sunlight penetrates, leaving the world in complete darkness. Here, marine life becomes sparse, but remarkable species still exist. At 1,300 meters, we find the leatherback turtle, the largest species of sea turtle, with a soft shell. These turtles lay eggs on beaches but return to these deep waters. At this depth, we also encounter the goblin shark, a terrifying creature whose appearance resembles that of a mythical goblin. The shark's jaw can extend outward to catch prey, resembling the xenomorph from Alien. Its eerie bite can be more frightening than lethal. At 1,700 meters, we find an unexpectedly charming resident, the southern elephant seal, the largest species of seal. These seals have large, distinctive noses and can dive to incredible depths. A fully grown southern elephant seal can weigh up to 5 tons and reach lengths of nearly 7 meters. And yet, the journey into the depths has only just begun. What lies even further below? Stay tuned to explore the mysteries of the abyss. Let's continue diving to a depth of 2,000 meters. At this terrifying depth, there lives a creature called the black dragonfish. This fish truly looks like it belongs on another planet. Its black has sharp teeth and a barbel dangling beneath its chin that resembles a glowing bulb. The light from the bulb lures prey, which the dragonfish then ambushes and devours in the darkness. Now, let's dive deeper, to 3,000 meters. At this depth, we enter the midnight zone, where the temperature drops to just 1 to 2 degrees Celsius. There's complete darkness and the water pressure exceeds 300 atmospheres. Fish are scarce at this level, but there's one giant creature that thrives here, the sperm whale. While it's not a fish, it's the deepest diving marine mammal known. Sperm whales dive to this depth to hunt giant squid, which are their favorite prey. A sperm whale can hold its breath for over an hour, diving deep to find and capture these squid. How do we know there are so many giant squid in the deep ocean? By studying the stomachs of sperm whales, when dissected, the whale's stomachs are often filled with squid beaks, the only hard, indigestible part of their bodies. These remnants tell us that sperm whales consume an estimated 5 million giant squid annually, suggesting there's an abundant population of these elusive creatures in the depths. So why are they called sperm whales? The name comes from the word spermicidae, a waxy substance found in the whale's head that was historically used to make candles and perfumes. This substance, along with the squid in their diet, contributed to their name and value in the past. Let's continue diving to 3,800 meters. Here lies the wreck of the Titanic, which sank in 1912 along with Jack and Rose's story. The Titanic rests at this depth, preserved as a UNESCO underwater cultural heritage site, and no longer permitted to be salvaged. To visit it, you need to master deep-sea diving. Director James Cameron, who filmed the movie Titanic, has visited the wreck an astounding 33 times. Descending further to 4,000 meters, we encounter the fontou fish, a deep-sea predator with exceptionally long, sharp teeth. In the food-scarce environment of the deep sea, these fish cannot afford to lose a meal, so their teeth are perfectly adapted to grasp and hold on to any prey they catch. At 6,000 meters, we enter the hadal zone, or the trenches of the ocean. In 1989, Japan's Shinkai 6500 submersible reached 6,500 meters. Later, in 2012, China's Jialong submersible went even deeper, reaching 7,000 meters. The deepest fish ever discovered, a species of Mariana snailfish, was found at 8,178 meters in 2017 by Chinese and Japanese research teams. These fish, pale and fragile, were observed eating shrimp bait provided by researchers. At a depth of 10,660 meters, scientists discovered a giant single-celled organism measuring up to 20 centimeters long. This massive cell is a fascinating relic from the ancient past, giving us a glimpse of how life might have existed billions of years ago. Finally, we reach the deepest part of the ocean, the Challenger Deep in the Mariana Trench, at a staggering 11,034 meters. The trench's depth was first measured in the 1950s using explosive sound waves. Since then, only four people have visited this extreme environment, fewer than those who have walked on the moon. The first descent was in 1960, undertaken by Don Walsh and Jacques Piccard in the Bath Escape Trieste. It took them five hours to reach the seafloor, only to find a window crack upon arrival, forcing them to resurface. Before ascending, they reported seeing flatfish and shrimp at this depth. The next visit wasn't until 2012, when James Cameron descended solo in the Deep Sea Challenger. Spending over two hours at the bottom, Cameron observed only small, shrimp-like creatures in what he described as a barren, lunar-like landscape. In 2019, explorer Victor Vescovo visited the Challenger Deep twice, in two months. He reported seeing little except for plastic waste, including garbage bags. From flatfish in 1960 to just shrimp in 2012, and now plastic in 2019, human impact on even the deepest parts of the ocean is undeniable. Exploring these depths not only helps us understand the limits of life on Earth, but also sheds light on the potential for life in the universe. If organisms can survive under such immense pressure without light, perhaps extraterrestrial life might thrive in similarly extreme conditions, such as under the icy crust of moons like Europa or Enceladus. Water remains the key to life as we know it. While life cannot survive without water, some microorganisms can endure in a state of suspended animation. Without water, they stop all metabolic activity and appear dead, but just a drop of water can bring them back to life. Maybe, one day, we'll find life beyond Earth. And maybe, all it will take is a single drop of water to awaken it. Thank you for watching. If you enjoyed this video, don't forget to like and subscribe.