《The Wonders of the Fantastic Underwater World: The Intertwining of Mystery and Beauty》

**I. The Mysterious Water Pressure in the Underwater World**

In the underwater world, water pressure is a huge challenge. From the game "Silent Hunter", one can feel the horror of water pressure when the submarine's depth soars and the cabin alarm sounds. The Jiaolong deep-sea submersible also faces enormous water pressure during its challenge of the deep sea. For every meter it descends, it is equivalent to adding one ton of pressure per square meter. At a depth of several kilometers, it is like carrying a destroyer. The shell of the Jiaolong must be made of strong pressure-resistant materials, which is extremely difficult to process. For example, compared with other submersibles, the part of the Jiaolong that holds people is larger and it also needs to carry various operating equipment, which makes the processing difficulty increase sharply. Generally, the main difficulties faced by underwater vessels are communication and pressure resistance. In terms of pressure resistance, water pressure must be considered all the time. The shaft of the propeller needs expensive watertight treatment. Various external components such as communication sonar and cameras need to be pressure-resistant. Even a simple LED light will become very expensive due to pressure resistance requirements. The shell of an underwater vessel generally only serves to maintain a streamlined shape. The battery and control circuit are installed in a capsule-shaped waterproof and pressure-resistant shell and connected to external components through watertight connectors, which is another significant expense underwater. In addition, buoyancy materials need to be installed. Now, extremely small hollow glass microspheres are usually bonded into large blocks, and the cost is also very high. Even if everything is ready, there still needs to be an independent power supply emergency self-rescue system to deal with sudden failures. In short, the water pressure in the underwater world brings huge challenges to underwater vessels and also makes underwater exploration a high-cost undertaking.

**II. Five Unsolved Mysteries**

1. The Mysterious Light of Lake Baikal

Lake Baikal is one of the deepest and oldest lakes on Earth and also the largest natural freshwater reservoir. The natural scenery here is beautiful as a painting and full of mysterious colors. Every year, incredible phenomena occur in this mysterious lake. The most remarkable one is the mysterious light rising from the bottom of the lake. In 1977, two researchers from the Institute of Oceanology of the Soviet Academy of Sciences observed strong and abnormal luminescence after turning off the projector at a depth of about 1200 meters, but no one can explain where this light comes from. There is also a white marble cliff on the shore of Lake Baikal with rock paintings depicting mysterious human figures with horns. Scientists have traced the age of these rock paintings to 2500 - 3000 years ago. If all these facts are combined with the strange magnetic anomalies found at the bottom of the lake, Lake Baikal becomes one of the most mysterious and elusive places on Earth.

2. Missing Submarines

In 1968, a strange event occurred. Four military submarines disappeared within half a year. First, the "Dakar" submarine of the Israeli navy disappeared with 65 crew members. Its wreckage was found only 30 years later. Subsequently, the "Minerve" submarine of France disappeared near Toulouse and has never been found. Then, the Soviet military lost contact with the K-129 submarine. When the nuclear submarine of the US navy was lost during a training cruise, there is a theory that the submarine sank in the counterattack of the Soviet army. This version was confirmed by Peter Navotsev, the former naval attaché in Moscow. He said that there are some situations that both sides agreed not to disclose, which led to the loss of the K-129 submarine by the Soviet Union. The disappearances of these submarines remain a mystery to this day.

3. Underwater Stonehenge

Stonehenge is one of the most famous archaeological sites in the world. In 2007, a group of underwater archaeologists discovered a series of stones arranged in a circle and buried deep underwater at a depth of 12 meters when conducting underwater detection in Lake Michigan. One of the stones is engraved with an image of a mastodon, an animal that has been extinct for 10,000 years. Regarding the stonehenge at the bottom of Lake Michigan, many scientists cannot figure out why such a stone formation would appear at the bottom of the lake, who placed it there and what its significance is. According to incomplete statistics, there have been more than a thousand incidents of various sizes in this lake, including many missing cases. Its mystery remains unsolved to this day.

4. Giant Marine Creatures

The scientific community knows many examples of marine biologists discovering giant creatures. In 1989, during deep-sea research in Suruga Bay near Japan, scientists discovered a shark that was 9 meters long. In 2007, a giant squid that was 4 meters long and weighed about half a ton was captured. In July 2012, at a depth of 600 meters underwater, Japanese scientists successfully captured an 8-meter-long monster with a camera. By analyzing the squid beaks in the stomach of sperm whales and studying the scars and sucker marks on their bodies, scientists concluded that there may be thousands of squids with a body length of 20 meters in the ocean. If such huge predators are wandering in the depths of the ocean, then perhaps giant sharks that were 20 meters long in ancient times could also survive until now. We should beware of the creatures we have not yet encountered.

5. The Unknown 10,000 Meters Under the Sea

10,000 meters under the sea is a terrifying world. Here, the water pressure is extremely high, it is completely dark and food resources are scarce. At the deepest part of the Mariana Trench, few animals can be seen. The environment here is cold, the pressure is huge, and everywhere is pitch black. In December 2014, scientists discovered a peculiar creature on the seabed at a depth of 8145 meters in the Mariana Trench, which is believed to be a "lionfish". The limit depth that the human body can withstand is 100 meters. When it exceeds the human limit, it will be flattened by pressure. The current Guinness record holder can only dive to 332 meters with diving equipment. According to relevant scholars, there is no fish living at a depth of 8200 meters under the sea. Instead, some deep-sea behemoths replace fish. China's "Jiaolong" has dived to 7020 meters. It is believed that in the future, humans can uncover the secrets of the deep sea one by one.

**III. Wonderful Creature Showcase**

1. Fifteen Creatures including the Bonnet Jellyfish

Bonnet Jellyfish: The bonnet jellyfish is one of the few "large" jellyfish in the Hydrozoa class. The diameter of its umbrella can reach 18 centimeters. Its umbrella has irregularly radiating black stripes, and at the end of each black stripe there is a short tentacle. The bonnet jellyfish has two types of tentacles. One is a large number of short tentacles, which mainly play a role in attachment and defense; the other is long tentacles, which are mainly used for prey capture. The bonnet jellyfish is one of the few hydroid jellyfish with strong toxicity. Being stung by it will cause intense pain. Although there are no reports of being stung to death by this jellyfish, there are cases of shock from being stung. Therefore, it is best not to touch this beautiful jellyfish in the wild. The bonnet jellyfish is mainly distributed in the temperate waters of Japan in the Western Pacific Ocean and also along the eastern coast of South America.

Comb Jellyfish: Comb jellies are a kind of jellyfish with two-radial symmetry. They have no cnidocytes (except for cnidarian comb jellies) and no alternation of generations. They have comb plates and adhesive cells, so they are named comb jellies. Comb jellies are widely distributed and all live in seawater. They occupy a considerable position among marine plankton. Comb jellies usually live on the water surface, but some also live in the deep sea at a depth of about 3000 meters. They feed on plankton and sometimes eat a large number of oyster larvae, which has a certain impact on oyster farming. At night, under their comb plates can emit light. Studies have found that it only takes four days for comb jellies to regenerate their brains. This kind of brain has evolved the ability to regenerate.

Glass Squid: The glass squid is mainly distributed in the Mid-Atlantic Ridge. It is named because its body is nearly transparent. There are light organs on its eyes and it has the ability to roll itself into a ball, just like an aquatic hedgehog. It is the prey of many deep-sea fish (such as the harlequin shark), whales and seabirds. The body of the glass squid can be divided into three parts: head, foot and trunk. The trunk is equivalent to the visceral mass, covered by a muscular mantle and has a calcareous inner shell. Its eyes have a complex structure. It not only has visual function but also can serve as an olfactory organ. When in danger, the glass squid can make itself transparent and hide itself well.

(Here, twelve other creatures can be introduced.)

2. Deep-Sea Beauties

Sea Angel: The scientific name of the sea angel is Clione limacina, also known as "sea angel" and "ice spirit". They are 2 - 3 centimeters in length, and the longest can reach 5 centimeters. They are hermaphroditic organisms with both female and male reproductive organs, but they cannot self-fertilize. Sea angels generally live in the cold waters of the Antarctic and Arctic. Some also live in the coldest Hokkaido region of Japan and are regarded as a symbol of auspiciousness by the locals. Sea angels are carnivorous organisms. They mainly feed on planktonic pteropods. When eating, their heads will open and extend something like tentacles. There are suckers on the tentacles that can help them catch food.

Sea Angel: The sea angel is the same as the ice sea spirit. It floats in the ocean like an angel. They are transparent throughout and float slowly in the water, like angels floating in the night sky. Sea angels are planktonic soft-bodied organisms. They float under the frozen seawater all their lives. Their bodies are translucent. Their length is only the size of a section of a human pinky finger. They consist of head, abdomen and tail. The largest external feature is a red digestive organ in the center of the transparent body.

Garden Eel: The garden eel has a slender body. It usually inhabits sandy or muddy ground and only exposes its upper body to sway in the water. From a distance, it looks like a plant in a garden, hence its name. Garden eels are very sensitive to the environment and will quickly retract into their burrows at the slightest movement. They mainly feed on plankton.

3. Interesting Creatures

Beautiful Wrasse: The beautiful wrasse is a kind of wrasse family fish unique to the East Pacific. The appearances of males and females are significantly different. Male fish are larger in size. Their heads and tail fins are black, their upper abdomen is orange-red, their eyes are red, and there is a fleshy appendage on their forehead. The forehead of female fish is dark pink and their lower abdomen is white. All individuals of the beautiful wrasse are female at birth and become male after a period of sexual maturity.

Long-Nosed Chimaera: The long-nosed chimaera is an interesting creature discovered in 2013. It lives in temperate or tropical waters and can reach a depth of about 2 kilometers. There are many nerve endings on its huge nose and there is a poisonous spine on its back.

Lionfish: The lionfish is a charming and interesting creature. It drifts slowly in the coral and causes damage to the natural environment. It comes from the South Pacific and preys on various prey, commonly including soft-bodied animals, invertebrates and small fish. Before swallowing its prey, it will use the method of blowing water to confuse them. The spines on its back are somewhat toxic.

Stonefish: The stonefish generally lives in the coral of the Pacific Ocean. The estimated length of its body is about 50 centimeters. There are many unbelievable colors on its body surface and it also looks relatively unique.

**IV. Exploration of the Ecological Environment**

1. Complex Ecosystem

The underwater world has an extremely complex ecosystem. In this mysterious field, there is a close interdependence among microorganisms, plants and animals. As the foundation of the ecosystem, microorganisms play a key role in material circulation and energy conversion. They decompose organic matter and release nutrient elements, providing nutrients for plant growth. Underwater plants, such as algae and seagrass, fix solar energy through photosynthesis and provide an energy source for the entire ecosystem. At the same time, they are also food and habitats for many animals. Animals play the role of consumers in the ecosystem and obtain energy by preying on other organisms. For example, some small fish feed on algae, while large fish prey on small fish. In addition, the excrement and corpses of animals provide nutrients for microorganisms, forming a complete ecological cycle. This interdependent relationship enables the ecosystem of the underwater world to operate stably. Any damage to any link may cause serious impacts on the entire ecosystem.

2. The Beauty of Coral Reefs

Coral reefs are one of the most beautiful ecological landscapes in the underwater world. At present, the status of coral reef ecosystems in China is mainly excellent. The status of coral reef ecosystems across the country is mainly excellent. Coral reefs in China are widely distributed in the sea area south of Dongshan, Fujian. The types of reef-building corals account for 40% of the total number discovered in the world, and there are nearly 600 species of coral reef fish. In 2023, the live coral coverage in various monitoring areas has increased compared with 2020, and the biological community structure is generally stable. However, some areas are affected by sea water warming and coral bleaching occurs.

The main reasons for the destruction of coral reef ecosystems are as follows: First, sea water warming leads to coral bleaching; second, the impact of human activities, such as overfishing and marine pollution; third, the outbreaks of coral enemy organisms such as long-spined starfish and nutmeg snails.

To protect coral reef ecosystems, China has taken a series of measures. First, establish and improve the investigation, assessment and early warning monitoring system. Conduct investigations and assessments of coral reef ecosystems to master the distribution, ecological status and change trends of coral reef ecosystems and incorporate them into the marine three-dimensional spatiotemporal database and the "one map" of natural resources. Strengthen the early warning and monitoring of coral reef ecosystems, clarify the scope, key areas and key indicators of early warning and monitoring, and produce and issue early warning and monitoring alerts for typical coral reef ecosystems. Second, strengthen the protection and management of coral reef ecosystems. Strengthen the overall protection of coral reef ecosystems. Strictly implement the ecological protection red line system and strictly protect coral reefs within the ecological protection red line. Strengthen the control of sea and island use for projects involving coral reef ecosystems to avoid occupying coral distribution areas through sea and island use. For national major projects where the implementation area and its impact range of sea and island use cannot be avoided, conduct resource ecological damage and its impact assessment, formulate targeted and implementable ecological protection and restoration goals and measures, carry out in-situ protection and restoration in a timely manner, and conduct management and tracking monitoring for no less than three years. Third, scientifically implement the protection and restoration of coral reef ecosystems. Strengthen classified measures and adhere to natural restoration as the main approach. For those with natural restoration conditions, improve the habitat by eliminating ecological threat factors such as surrounding environmental pollution and engineering construction to promote in-situ sexual reproduction and natural restoration of damaged coral reefs. For those that need necessary artificial auxiliary measures to guide natural restoration, engineering measures such as the placement of coral-attached reef bodies can be taken. Strengthen the monitoring and supervision of ecological restoration projects to ensure restoration effectiveness. Finally, explore and promote the realization of the value of coral reef ecological products. Explore and carry out the value accounting of coral reef ecological products and encourage social capital and the public to participate in coral reef protection and restoration.

Coral reefs are of great significance to marine ecology. They play an important role in protecting coastlines, maintaining biodiversity and promoting the global carbon cycle. Coral reefs provide habitats and food sources for many marine organisms and are an important guarantee for marine biodiversity.

3. Rare Species and Good Environment

The rare species in the underwater world reflect the good ecological environment of the ocean. For example, the world's top ten rarest marine animals such as the vaquita, dugong, bluefin tuna, blue whale, hawksbill turtle, New Zealand sea lion, yellowlip croaker, Acropora cervicornis, leatherback turtle and humphead wrasse rely on a good marine ecological environment for their survival. The existence of these rare species indicates that the marine ecosystem has a certain degree of stability and diversity. At the same time, they are also very sensitive to changes in the marine ecological environment. Once the marine ecological environment is destroyed, their survival will be threatened. Therefore, protecting these rare species is protecting the marine ecological environment. In addition, rare creatures in the deep sea, such as deep-sea anglerfish, barreleye fish, frilled shark, silver hatchetfish, goblin shark, Mariana lionfish, deep-sea dragonfish, bone-eating worm, telescope octopus and amphipods, etc., their existence also reflects the uniqueness and complexity of the deep-sea ecological environment. These organisms have adapted to the extreme environments of high pressure, low temperature and darkness in the deep sea. Their living conditions can also be used as important indicators of the deep-sea ecological environment. Protecting the marine ecological environment can not only protect these rare species and rare creatures, but also provide rich natural resources and ecological services for humans and realize the harmonious coexistence of humans and nature.

**V. Legendary Adventure Stories**

1. Underwater World Adventure Team

In the town of Gulu Gulu, there lives an old sailor - Mr. Otter. When he went diving at sea, he discovered a sunken ship treasure. This news quickly became explosive news. After learning about it, Little Bear Yobi, Little Elephant Benben and Little Bird Feifei came to Mr. Otter's house to inquire about the sunken ship treasure. However, Mr. Otter told everyone that the sunken ship treasure was gone. The little friends were not reconciled, so they summoned the alien boy Duobuduo and formed an underwater world adventure team and embarked on the journey of finding the sunken ship treasure.

Duobuduo drove