• Seas are smaller than oceans and located where land and ocean meet. They have great geographical, political, and economical significance.
• Marginal seas are seas partially enclosed by islands, archipelagos, or peninsulas. Such seas include Arabian Sea, Baltic Sea, Bay of Bengal, Bering Sea, Black Sea, Gulf of California, Gulf of Mexico, Mediterranean Sea, Red Sea, and all four Siberian Seas.
• The primary differences between marginal seas and open oceans are associated with depth and proximity to landmasses. Marginal seas are shallower than open oceans and are influenced more by human activities, river runoff, climate, and water circulation than open oceans.

Important Seas of the World

Arabian Sea

• The Arabian Sea is a region of the northern Indian Ocean.
• It is bounded on the north by Pakistan, Iran, and the Gulf of Oman.
• On the west, it is bounded by the Gulf of Aden, Guardafui Channel, and the Arabian Peninsula.
• The Laccadive Sea bounds it on the southeast, the Somali Sea on the southwest, and India on the east.
• The Gulf of Aden in the west connects the Arabian Sea to the Red Sea through the strait of Bab-el-Mandeb.
• The Gulf of Oman is in the northwest, connecting it to the Persian Gulf.
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Andaman Sea

• The Andaman Sea is a marginal sea of the northeastern Indian Ocean.
• It is bounded by the coastlines of Myanmar and Thailand along the Gulf of Martaban.
• The west side of the Malay Peninsula also bounds it.
• The Andaman Islands and the Nicobar Islands separate it from the Bay of Bengal to its west.
• Its southernmost end is defined by Breueh Island.
• It communicates with the Malacca Strait.
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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.
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East China Sea

• The East China Sea is a marginal sea of the Western Pacific Ocean.
• It is located directly offshore from East China.
• The Japanese islands of Kyushu and the Ryukyu Islands are towards the east of this sea.
• The South China Sea is towards the south of it.
• The Asian continent bounds it to the west.
• 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.
• Tensions between China and Japan have risen over the contested Senkaku/Diaoyu islands that lie in this sea.
• 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.
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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.
• The Kuril Islands are stretched from the Japanese island of Hokkaido to the southern tip of Russia’s the Kamchatka Peninsula.
• They separate the Okhotsk Sea from the North Pacific ocean.
• The Kuril Islands consist 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.
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Adriatic Sea

• The Adriatic Sea is a part of the Mediterranean Sea.
• It is 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.
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• 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.

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 is bordered by Turkey, and by Bulgaria, Romania, Ukraine, Russia, and Georgia.
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Caspian Sea

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

• 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.
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Caribbean Sea

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

• The Gulf of Mexico is a partially landlocked body of water in North America.
• It is located on the southeastern periphery of the continent.
• It is connected to the Atlantic Ocean by the Straits of Florida, which run between the peninsula of Florida and the island of Cuba.
• It is connected to the Caribbean Sea by the Yucatán Channel, which runs between the Yucatán Peninsula and Cuba.
• Dead Zone:
  • Dead zones are hypoxic areas in oceans and lakes.
  • The Gulf of Mexico has the second-largest dead zone in the world.
  • The dead zone in the Gulf of Mexico is fueled by nutrient-laden water from the Mississippi River.
  • It blooms every summer due to warming waters and the acceleration of microorganisms’ metabolisms.
  • The dead zone is expected to worsen as the climate continues to change.
  • 

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
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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.
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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.
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Tasman Sea

• The Tasman Sea is a marginal sea of the South Pacific Ocean.
• It is situated between Australia and New Zealand.
• It was named after the Dutch explorer Abel Janszoon Tasman.
• Tasman 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.
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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