In terms of geography, Seas are smaller than oceans and are usually located where the land and ocean meet. Typically, Seas are partially enclosed by land. Seas have great geographical, Political, and Economical significance.

In oceanography, a marginal sea is a sea partially enclosed by islands, archipelagos, or peninsulas.

Some of the major marginal seas include the Arabian Sea, Baltic Sea, Bay of Bengal, Bering Sea, Black Sea, Gulf of California, Gulf of Mexico, Mediterranean Sea, Red Sea, and all four of the Siberian Seas (Barents, Kara, Laptev, and East Siberian).

The primary differences between marginal seas and open oceans are associated with depth and proximity to landmasses. Marginal seas, which are generally shallower than open oceans, are more influenced by human activities, river runoff, climate, and water circulation.

Major (Important) Seas of the world

  1. Arabian Sea
  2. South China Sea
  3. East China Sea
  4. Coral Sea
  5. Caribbean Sea
  6. Mediterranean Sea
  7. Ionian Sea
  8. Bay of Bengal
  9. Arabian Sea
  10. Bering Sea
  11. Sea of Okhotsk
  12. Gulf of Mexico
  13. Tasman Sea
  14. Hudson Bay
  15. Sea of Japan
  16. Sea of Azov
  17. Caspian Sea
  18. Adriatic Sea
  19. Baltic Sea
  20. Red Sea
  21. Yellow Sea
  22. Dead Sea
  23. Black Sea
  24. Tyrrhenian Sea
  25. Ligurian Sea
  26. Balearic Sea
  27. Alboran Sea
  28. Sargasso Sea
  29. The Aegean Sea…

Arabian Sea

The Arabian Sea is a region of the northern Indian Ocean bounded on the north by Pakistan, Iran, and the Gulf of Oman, on the west by the Gulf of Aden, Guardafui Channel, and the Arabian Peninsula, on the southeast by the Laccadive Sea, on the southwest by the Somali Sea, and on the east by India.

The Gulf of Aden in the west connects the Arabian Sea to the Red Sea through the strait of Bab-el-Mandeb, and the Gulf of Oman is in the northwest, connecting it to the Persian Gulf.

arabian sea

Andaman Sea

The Andaman Sea (historically also known as the Burma Sea) is a marginal sea of northeastern Indian Ocean bounded by the coastlines of Myanmar and Thailand along the Gulf of Martaban and west side of the Malay Peninsula and separated from the Bay of Bengal to its west by the Andaman Islands and the Nicobar Islands.

Its southernmost end is defined by Breueh Island, an island just north of Sumatra, and communicates with the Malacca Strait.

Andaman sea

South China Sea

Places here are China, Vietnam, Hainan, Malaysia, and the Philippines. China is involved in disputes with many countries here. Places in dispute are Paracel, Scarborough Shoal, and The Spratly Islands.

South China Sea

East China Sea

The East China Sea is a marginal sea of the Western Pacific Ocean, located directly offshore from East China.

Towards the east of this sea are the Japanese islands of Kyushu and the Ryukyu Islands, towards the south of it is the South China Sea and to the west by the Asian continent. The sea connects with the Sea of Japan through the Korea Strait and opens to the north into the Yellow Sea. The countries which border the sea include South Korea, Japan, the Republic of China (Taiwan) and the People’s Republic of China.

In recent times, tensions between China and Japan have risen over the contested Senkaku/Diaoyu islands that lies in this sea, and both nations have raised as incursions into the disputed waters. Both countries have increased their military capabilities, particularly their radar and missile systems, in the region.

east china sea map
east china sea

Sea of Okhotsk

  • The Sea of Okhotsk is a marginal sea of the western Pacific Ocean.
  • It is located between Russia’s Kamchatka Peninsula on the east, the Kuril Islands on the southeast, Japan’s island of Hokkaido on the south, the island of Sakhalin along the west, and a stretch of eastern Siberian coast along the west and north.
  • Kuril Islands
    • The Kuril Islands are stretched from the Japanese island of Hokkaido to the southern tip of Russia’s the Kamchatka Peninsula separating the Okhotsk Sea from the North Pacific ocean.
    • It consists of 56 islands and minor rocks.
    • The chain is part of the belt of geologic instability circling the Pacific and contains at least 100 volcanoes, of which 35 are still active, and many hot springs.
    • Earthquakes and tidal waves are common phenomena over these islands.
Sea of Okhotsk upsc

Adriatic Sea

  • The Adriatic Sea is a part of the Mediterranean Sea positioned between the eastern coastline of Italy, and countries of the Balkan Peninsula, from Slovenia, South through Croatia, Montenegro, and to Albania.
    • The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan Peninsula.
    • The countries with coasts on the Adriatic are Albania, Bosnia and Herzegovina, Croatia, Italy, Montenegro, and Slovenia.
Adriatic Sea

Dalmatian coastline

  • Dalmatia is one of the four historical regions of Croatia, alongside Croatia proper, Slavonia, and Istria. Dalmatia is a narrow belt of the east shore of the Adriatic Sea, stretching from the island of Rab in the north to the Bay of Kotor in the south.
dalmatian coast geography

Black Sea

The Black Sea is an inland sea located between far-southeastern Europe and the far-western edges of the continent of Asia and the country of Turkey. It’s bordered by Turkey, and by Bulgaria, Romania, Ukraine, Russia, and Georgia.

Black Sea

The Caspian Sea

The Caspian Sea is an enclosed body of water between Asia and Europe. It is bordered by Iran, Turkmenistan, Kazakhstan, Azerbaijan, Russia.

The Caspian Sea

Mediterranean Sea

The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Southern Europe and Anatolia, on the south by North Africa, and on the east by the Levant.

Mediterranean Sea

Sargasso Sea

  • While all other seas in the world are defined at least in part by land boundaries, the Sargasso Sea is defined only by ocean currents.
  • It is bounded on the west by the Gulf Stream, north, by the North Atlantic Current, east, by the Canary Current, and south, by the North Atlantic Equatorial Current.
  • This system of ocean currents forms the North Atlantic Gyre.
  • It is the only sea on Earth which has no coastline.
Sargasso Sea

Caribbean Sea

  • The Caribbean Sea is a tropical sea in the Western Hemisphere, part of the Atlantic Ocean, southeast of the Gulf of Mexico.
  • The Caribbean Sea is bordered by Venezuela, Colombia, and Panama to the south, Central American countries (Costa Rica, Nicaragua, Guatemala, Honduras, and Belize) on the west; with the Greater Antilles (Cuba, Jamaica, the Dominican Republic, and Puerto Rico) on the north and the Lesser Antilles on the east.
  • Anguilla
    • It is an island in the eastern Caribbean Sea and a British overseas territory.
Caribbean Sea UPSC

Gulf of Mexico

  • Gulf of Mexico is a partially landlocked body of water on the southeastern periphery of the North American continent.
  • It is connected to the Atlantic Ocean by the Straits of Florida, running between the peninsula of Florida and the island of Cuba, and to the Caribbean Sea by the Yucatán Channel, which runs between the Yucatán Peninsula and Cuba.
  • Dead Zone
    • Dead zones are hypoxic (low-oxygen) areas in the world’s oceans and large lakes.
    • The dead zone in the Gulf of Mexico, fueled by the nutrient-laden water spilling from the mouth of the Mississippi River, is the second-largest in the world.
    • It blooms every summer when warming waters accelerate the metabolisms of microorganisms, and it is expected to get even worse as the climate continues to change.
gulf of mexico

Red Sea

  • The Red Sea (Erythraean Sea) is a seawater inlet of the Indian Ocean, lying between Africa and Asia.
  • The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden.
  • To the north lie the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez (leading to the Suez Canal).
  • The sea is underlain by the Red Sea Rift which is part of the Great Rift Valley.

The six countries bordering the Red Sea are:

  • Saudi Arabia
  • Yemen
  • Egypt
  • Sudan
  • Eritrea
  • Djibouti
Red Sea

The Ionian Sea

  • The Ionian Sea is an elongated bay of the Mediterranean Sea, south of the Adriatic Sea.
  • It is bounded by Southern Italy to the west, southern Albania to the north, and the west coast of Greece.
Ionian Sea

Coral Sea

  • The Coral Sea takes its name from its coral formations of the Great Barrier Reef, the largest known reef system in the world.
Coral Sea UPSC

Tasman Sea

  • The Tasman Sea is a marginal sea of the South Pacific Ocean, situated between Australia and New Zealand.
  • The Tasman Sea was named after the Dutch explorer Abel Janszoon Tasman, who was the first recorded European to encounter New Zealand and Tasmania.
  • The British explorer Captain James Cook later extensively navigated the Tasman Sea in the 1770s as part of his first voyage of exploration.
Tasman Sea UPSC
Important Seas of the World

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Marginal Seas of the Arctic Ocean

  • Barents Sea
  • The Irish Sea

Marginal Seas of the Atlantic Ocean

  • Argentine Sea
  • Caribbean Sea
  • English Channel
  • Gulf of Mexico
  • Hudson Bay
  • Irish Sea
  • Labrador Sea
  • Mediterranean Sea
  • North Sea
  • Norwegian Sea
  • Scotia Sea

Marginal Seas of the Indian Ocean

  • Andaman Sea
  • Arabian Sea
  • Bay of Bengal
  • Java Sea
  • Persian Gulf
  • Red Sea
  • Sea of Zanj

Marginal Seas of the Mediterranean Sea

  • Adriatic Sea
  • Aegean Sea

Marginal Seas of the Pacific Ocean

  • Bering Sea
  • Celebes Sea
  • Coral Sea
  • East China Sea
  • Philippine Sea
  • Sea of Japan
  • Sea of Okhotsk
  • South China Sea (another important conflict zone)
  • Tasman Sea (between Australia and New Zealand)
  • Yellow Sea (by the Korean Peninsula)

Other Seas

  • The Caribbean Sea is sometimes defined as a marginal sea, sometimes as a Mediterranean sea.
  • The Caspian Sea is also sometimes defined as a marginal sea, and also the Dead Sea.

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