The 10 Largest Seas in the World

December 13, 2023

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Tropical island surrounded by clear blue water

Water makes up about 71 percent of the Earth’s surface. Around three percent of this water is found in rivers and lakes, glaciers, and below the ground, with 97 percent held in the world’s oceans and seas.

But what are the largest seas in the world ranked by area? Keep reading to find out.

1. Philippine Sea

Sunbeds on a beach in the Philippines
Sandy beach in the Philippines looking out on the Philippine Sea
Area: 5,695,000 km² (2,198,852 sq mi)
Average Depth: 6,000 m (19,700 ft)
Maximum Depth: 10,539 m (34,578 ft)

With a surface area of 5,695,000 square kilometers, the Philippine Sea is the largest sea in the world. Its deepest point is the Philippine Trench, which plunges to 34,578 feet.

Part of the Pacific Ocean, the Philippine Sea, lies east and north of the Philippines, with Japan to the north and Taiwan to the west.

The Philippine Sea is characterized by its many sea mountains, which rise from the basin floor and have coral-covered peaks. Because these seamounts attract an abundance of marine life, they are the sites of fishing grounds, along with areas near reefs and ridges and in the sea’s currents.

The sea is also known for its typhoons, which are particularly strong in September.

2. Coral Sea

Colorful fish swimming in coral reef in an area in the Coral Sea
Fish swimming in coral reef in the Coral Sea
Area: 4,791,000 km² (1,849,815 sq mi)
Average Depth: 2,394 m (7,854 ft)
Maximum Depth: 9,140 m (29,990 ft)

The world’s second-largest sea is the Coral Sea, which has a surface area of 4,791,000 square kilometers. While the sea’s deepest point is in Bougainville, at 29,990 feet below sea level, it has an average depth of 7,854 feet.

Located in the South Pacific Ocean, the Coral Sea has Australia’s east coast to the west, Vanuatu and New Caledonia to the east, the Solomon Islands to the northeast, and New Guinea’s eastern coast to the north. 

As its name suggests, this sea has countless coral reefs, most notably the Great Barrier Reef, which is the largest reef system in the world and was declared a UNESCO World Heritage Site in 1981. Most of the sea is protected by the Australian Coral Sea Marine Park and French Natural Park of the Coral Sea, meaning fishing is restricted in many areas.

The Coral Sea’s natural beauty, abundance of bird and aquatic life, and warm, stable climate make it a popular tourist destination.

3. American Mediterranean Sea

White sandy beach on the Caribbean Sea
White sandy beach on the Caribbean Sea
Area: 4,200,000 km² (1,621,629 sq mi)
Average Depth: 2,216 m (7,270 ft)
Maximum Depth: 7,686 m (25,217 ft)

Measuring 4,200,000 square kilometers, the American Mediterranean is the world’s third-largest sea. Its average depth is 7,270 feet, but its maximum depth is much deeper, at 25,217 feet.

The American Mediterranean Sea spans numerous islands and islets, including Cuba, Jamaica, Hispaniola, and Puerto Rico.

Not to be confused with the Mediterranean Sea — which appears further down this list — the American Mediterranean Sea is a scientific name that’s been given to this body of water, the basins of which include the Caribbean Sea and the Gulf of Mexico.

4. Arabian Sea

Aerial view of a beach in India in the Arabian Sea
Aerial view of a beach in India in the Arabian Sea
Area: 3,862,000 km² (1,491,127 sq mi)
Average Depth: 2,734 m (8,970 ft)
Maximum Depth: 4,652 m (15,262 ft)

The fourth-largest sea in the world is the Arabian Sea, which has a surface area of 3,862,000 square kilometers. The sea’s average depth is 8,970 feet, plummeting to 15,262 feet at its deepest point. 

Sitting between the Arabian Peninsula, India, Iran, the Gulf of Oman, and Pakistan, the Arabian Sea is part of the Indian Ocean and is home to multiple islands including Astola Island, the Lakshadweep Islands, Masirah Island, and Socotra.

Since the third or second millennium BCE, the Arabian Sea has been an important trade route, with India’s Kochi, Mormugão, and Mumbai ports, Pakistan’s Port of Karachi and Port Qasim, Iran’s Chabahar Port, and Oman’s Port of Salalah among its major seaports.

5. Sargasso Sea

Sargasso seaweed washed up on a Caribbean beach
Sargasso seaweed on a beach
Area: 3,500,000 km² (1,351,358 sq mi)
Average Depth: 5,000 m (16,404 ft)
Maximum Depth: 7,000 m (22,966 ft)

At 3,500,000 square kilometers, the Sargasso Sea is the fifth-largest sea in the world. One of the deepest seas on this list, it is almost 23,000 feet deep in some places, and it has an average depth of more than 16,000 feet.

The Sargasso Sea has no land boundaries — instead, it is bounded by the Gulf Stream, North Atlantic, Canary, and North Atlantic Equatorial currents, with the island of Bermuda located in the west.

Christopher Columbus first mentioned the Sargasso Sea after crossing it in 1492 because its huge mass of free-floating seaweed indicated the proximity of land. Today, the sea is still characterized by its brown seaweed, as well as its calm and warm blue water, weak currents, low precipitation, and high evaporation — all of which distinguish it from other parts of the Atlantic Ocean. The sea’s mild conditions mean it is largely devoid of plankton, but the seaweed supports unique marine life, some of which is endemic to the area.

6. South China Sea

The South China Sea at sunset
Sun setting over the South China Sea
Area: 3,500,000 km² (1,351,358 sq mi)
Average Depth: 1,212 m (3,976 ft)
Maximum Depth: 5,016 m (16,457 ft)

A part of the western Pacific Ocean, the South China Sea, lies between South China, Taiwan, Vietnam, and the Philippines. It has more than 200 islands, some of which are submerged, and together with the East China Sea, it forms the China Sea.

The South China Sea’s weather is tropical and the water near the surface is relatively warm, at 70 degrees Fahrenheit (21°C) during the winter and 84 degrees Fahrenheit (29°C) during the summer when typhoons are frequent.

Around a third of the world’s shipping trade travels through the South China Sea.

7. Weddell Sea

Icebergs floating in the Weddell Sea
Icebergs floating in the Weddell Sea, Antarctica
Area: 2,800,000 km² (1,081,086 sq mi)
Average Depth: 500 m (1,640 ft)
Maximum Depth: 5,148 m (16,890 ft)

Located off the west coast of Antarctica, the Weddell Sea forms part of the Southern Ocean, lying partially within the Antarctic Chilean Territory and within the overlapping territorial claims of Argentina and the UK. 

The Weddell Sea is fringed by several ice shelves, the most notable of which is the massive Filchner-Ronne Ice Shelf, covering much of the southern section of the sea.

8. Caribbean Sea

The Caribbean Sea with a palm tree-covered tropical island
Tropical island in the Caribbean Sea
Area: 2,754,000 km² (1,063,325 sq mi)
Average Depth: 2,200 m (7,218 ft)
Maximum Depth: 7,686 m (25,217 ft)

In eighth place on the ten largest seas in the world list is the Caribbean Sea, which has a surface area of 2,754,000 square kilometers. The sea’s deepest point is the Cayman Trough in between Cuba and Jamaica, which descends 25,217 feet below the surface. 

Forming part of the Atlantic Ocean, the Caribbean Sea is located between Mexico, the Caribbean Islands, Cuba, and Central America.

When Spain began transporting vast silver shipments across the Caribbean Sea in the 1560s, pirates flourished in the region, thanks to the multiple islands and bays that provided convenient hideaways. 

Today, the Caribbean Sea is known for its Mesoamerican Barrier Reef — the second-largest barrier reef in the world after the Great Barrier Reef. 

9. Mediterranean Sea

View of the Mediterranean Sea from a clifftop on the Amalfi coast
Bird’s eye view of the Mediterranean Sea from the Amalfi Coast in Positano, Italy
Area: 2,510,000 km² (969,116 sq mi)
Average Depth: 1,500 m (4,900 ft)
Maximum Depth: 5,109 m (16,762 ft)

With a surface area of 2,510,000 square kilometers, the Mediterranean Sea is the ninth-largest sea on Earth. It has an average depth of 4,900 feet, and the deepest recorded point is in the Calypso Deep at 16,762 feet below sea level.

The Mediterranean is connected to the Atlantic Ocean, but it is almost completely enclosed by land. It is surrounded by the countries of Albania, Algeria, Bosnia and Herzegovina, Croatia, Egypt, France, Greece, Israel, Italy, Lebanon, Libya, Monaco, Montenegro, Morocco, Palestine, Slovenia, Spain, Syria, Tunisia, and Turkey, with the island countries of Malta and Cyprus located in the sea. There are many other islands in the Mediterranean Sea, the largest of which are Sardinia and Sicily.

The sea has long been an important trade and transport route and it continues to attract travelers. Tourists, in particular, flock to the Mediterranean for its mild water temperatures and sunny coastline.

10. Gulf of Guinea

Fishing boat in the Gulf of Guinea
Fishermen in the Gulf of Guinea 
Area: 2,350,000 km² (907,340 sq mi)
Average Depth: 3,743 m (12,280 ft)
Maximum Depth: 6,363 m (20,876 ft)

The last sea to make it onto this list is the Gulf of Guinea, which measures 2,350,000 square kilometers, has an average depth of 12,280 feet, and has a maximum depth of 20,876 feet.

With a coastline that stretches from Cape Lopez in Gabon to Cape Palmas in Liberia, the Gulf of Guinea is a part of the Atlantic Ocean. It contains multiple islands, including the Bioko, Príncipe, São Tomé and Annobón islands, which form part of the Cameroon line of volcanoes.

Overview: World’s Largest Seas

RankSeaArea (km²)Area (square miles)Average Depth (feet)Maximum depth (feet)
1Philippine Sea5,695,0002,198,85219,70034,578
2Coral Sea4,791,0001,849,8157,85429,990
3American Mediterranean Sea4,200,0001,621,6297,27025,217
4Arabian Sea3,862,0001,491,1278,97015,262
5Sargasso Sea3,500,0001,351,35816,40422,966
6South China Sea3,500,0001,351,3583,97616,457
7Weddell Sea2,800,0001,081,0861,64016,890
8Caribbean Sea2,754,0001,063,3257,21825,217
9Mediterranean Sea2,510,000969,1164,90016,762
10Gulf of Guinea2,350,000907,34012,28020,876

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