A sea is a saltwater body connected to the World Ocean and characterized by its unique hydrological regime, size, depth, climate, flora, and fauna. There are about 90 seas on Earth. Here are the five largest.
1. Tasman Sea
Opening the top five giant seas is the Tasman Sea, with an area of 3.3 million sq. km and depths reaching up to 6,000 meters. Its salinity ranges from 30 to 35 parts per thousand. The sea is located in the southwestern Pacific Ocean, separating New Zealand and Australia.
The sea is named after the explorer Abel Tasman, who was the first to reach the shores of New Zealand and Tasmania in the 17th century.
Since the Tasman Sea spans three climate zones, its weather, flora, and fauna vary. The northern part lies near the tropics, while the southern region has a cooler climate. The warm East Australian Current moderates temperature differences slightly, but surface waters in the north still heat up to 27°C in summer, while the southern areas only reach about 15°C. Occasionally, small icebergs from Antarctica drift into the southern part due to the Cold West Wind Current.
In the northern section, you can find atolls and islands with coral formations. Though algae are scarce, the biodiversity is still significant. The southern region is richer in marine vegetation, particularly krill. The Tasman Sea is home to many shark species, including the great white, mako, longfin, reef, and bottom-dwelling sharks. Other notable fish include tuna, swordfish, and sailfish.
2. Coral Sea
The Coral Sea spans an area of 4.7 million sq. km and is part of the Pacific Ocean, lying between New Guinea, Australia, and New Caledonia. Some sections are more than 9,000 meters deep. Its flora and fauna closely resemble that of the nearby Tasman Sea, with which it connects via the Tasman Bay to the south. The salinity of the two seas is also quite similar.
The sea gets its name from the abundance of coral reefs and islands, which once hindered ship navigation. It’s home to the Great Barrier Reef, the largest coral reef system on Earth, larger than the United Kingdom. The reef is a UNESCO World Heritage site and is even visible from space. The Coral Sea’s seabed and island structure are highly fragmented due to the region’s seismic activity.
The climate in the Coral Sea is consistently warm and subtropical, with water temperatures ranging from 19°C to 28°C year-round. Cyclones are common, and from December to March, heavy rains often occur. The sea boasts a rich diversity of life, including 1,500 species of fish, 26 species of whales and dolphins, and six species of sea turtles. The coral islands also attract numerous birds and marine species, making it a popular destination for tourists.
3. Arabian Sea
The third-largest sea on the planet, the Arabian Sea, is located in the northern Indian Ocean. It receives water from the Indus River. The sea covers an area of nearly 4.8 million sq. km, with some parts exceeding 5,000 meters in depth, though the average depth is around 3,000 meters, making it a favorite spot for divers.
Ancient sailors knew the Arabian Sea by various names, including the Erythraean, Green, Persian, Omani, and Indo-Arabian seas. Its coasts are bordered by India, Djibouti, the Somali Peninsula, Iran, Pakistan, and Yemen, with the Maldives situated on the periphery. The sea hosts major global trade routes and numerous important ports.
The Arabian Sea’s beaches are popular tourist destinations due to the pleasant climate and clean, salty waters. The entire sea lies in a tropical climate zone. In winter, the water never drops below 22°C, and in summer, it can reach up to 30°C, although there are areas where the water remains as cool as 12°C.
The Arabian Sea is known for its rich biodiversity. The large island of Astola (Pakistan) is home to rare species of sea turtles, such as the green turtle and hawksbill, which attract ecotourists.
4. Philippine Sea
The Philippine Sea is the largest marginal sea on Earth, covering about 5.7 million sq. km. Some areas are nearly 11,000 meters deep. It is located in the northern Pacific Ocean, near the Philippine Archipelago, and is named after it. The sea has no clear boundaries and is separated from the ocean by islands, including the Philippines, Honshu, Kyushu, Ryukyu, and Taiwan.
The sea is famous for containing the Mariana Trench, the deepest part of the world’s oceans, shaped like a crescent, with a depth of more than 2,500 km and a width of about 70 km. This trench is a U.S. national monument.
The Philippine Sea spans the subtropical, tropical, sub-equatorial, and equatorial climate zones, with only the subtropical zone experiencing notable seasonal differences. In winter, air temperatures vary from 9°C in the north to 27°C in the south. Strong winds, such as monsoons and trade winds, blow over the sea. The salinity is about 34.5 parts per thousand throughout the sea.
The Philippine Sea is abundant with marine life, including commercially valuable fish like tuna, which is caught in large quantities. It is also home to the whale shark, a rare and harmless species to humans, and the endangered dugong, a marine mammal.
5. Sargasso Sea
The Sargasso Sea, located in the Atlantic Ocean, is unique and recognized as the largest sea in the world, with an area between 6 and 7 million sq. km. The Bermuda Islands lie to the west. The Sargasso Sea has no shores, being bordered by four ocean currents: the Canary Current, Gulf Stream, North Atlantic Current, and North Atlantic Equatorial Current.
Despite its location in the North Atlantic, the Sargasso Sea is relatively warm, with temperatures reaching 18°C in winter and 28°C in summer. Its salinity is 37 parts per thousand. A large part of the sea’s surface is covered by thick mats of brown seaweed, called sargassum. Due to the movement of air and water currents in this area, the mass of aquatic plants slowly swirls in a clockwise direction.
The famous Portuguese explorer Christopher Columbus, who reached the Sargasso Sea in the 15th century, initially believed he had discovered new land due to the seaweed-covered surface resembling solid ground. Ships that sailed into the area would often get entangled in the seaweed, and some even disappeared without a trace.
Today, a significant portion of the sea is covered in garbage. Oceanographers emphasize the importance of preserving this unique natural environment and its specific flora and fauna.