What are facts about the sea?

1. Size: The surface area of the ocean covers approximately 71 percent of the Earth's surface, or about 361 million square kilometers (140 million square miles).

2. Depth: The average depth of the ocean is about 3700 meters (12,100 feet), but the deepest point is the Mariana Trench in the Pacific Ocean, which measures 11,034 meters (36,201 feet) deep.

3. Salinity: The average salinity of seawater is around 35 parts per thousand (ppt). This means that for every kilogram of seawater, there are about 35 grams of dissolved salts, mostly sodium chloride (common salt).

4. Waves: Ocean waves are caused by the transfer of energy from wind to the water's surface. The height and speed of waves depends on factors such as wind strength, distance over which the wind blows (fetch), and water depth.

5. Tides: Tides are the periodic rise and fall of the sea level caused by the gravitational pull of the moon and the sun. High tide occurs when the water level is at its highest, while low tide occurs when it is at its lowest.

6. Ocean Currents: Ocean currents are large bodies of water that move through the oceans. They are driven by various factors, including wind, the Coriolis effect (the deflection of moving objects due to the Earth's rotation), and density differences. Ocean currents play a crucial role in regulating the Earth's climate by transporting heat and nutrients.

7. Marine Life: The oceans are home to an incredible diversity of marine life, including fish, marine mammals, seabirds, reptiles, and invertebrates. It is estimated that there could be over a million marine species, many of which have yet to be discovered.

8. Coral Reefs: Coral reefs are underwater ecosystems composed of colonies of tiny animals called coral polyps. They provide habitat and food for a wide variety of marine life, making them one of the most biodiverse ecosystems on Earth.

9. Dead Zones: Dead zones are areas in the ocean where the oxygen levels are too low to sustain most forms of marine life. They are often caused by excessive nutrient pollution from human activities, such as agricultural runoff and sewage discharge.

10. Pollution: The ocean faces various forms of pollution, including plastic waste, oil spills, and chemical pollution. These pollutants can harm marine life, disrupt marine ecosystems, and pose risks to human health through the consumption of contaminated seafood.