These are the world's most heavily contested seas

The world is ultimately linked by its bodies of water. 

Global trade relies upon open navigation of the water ways and easy access around the globe.

However, the following seas have had their fair share of being fraught with tension. We have listed eight of the tensest seas in the world below. 

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Aegean Sea

Countries in Conflict: Greece and Turkey

Airspace violations between Greece and Turkey are a common issue between the two countries, especially over the Aegean Sea.

The island-filled stretch of water separating Turkey and Greece contains maritime boundaries that are a persistent source of disagreement between the two countries.

Although violations happen with frequency between the two countries, Turkey and Greece have seen a rapid increase in incidents since 2013.

Black Sea

Countries in Conflict: Russia, Ukraine, and NATO

The Black Sea has become a point of geopolitical tension following Russia's annexation of the Crimean peninsula and the conflict with Ukraine. In June 2015, a Russian Su-24 buzzed a US guided-missile destroyer that was operating in the sea raising tensions between the two countries. 

And earlier this month Ukraine and NATO member Turkey launched joint naval drills in the Black Sea as both countries face sharply deteriorating relations with Moscow.

Baltic Sea

Countries in Conflict: NATO and Russia

The Baltic Sea is ringed by NATO members, countries leaning towards NATO, and two Russian ports. Since Russia's annexation of the Crimean Peninsula and the start of the Ukraine crisis, tensions throughout the Baltics have steadily risen. 

Most recently, on April 12, two Russian aircraft repeatedly flew simulated attack patterns over a US naval ship. In response to the incident, US Secretary of State John Kerry said that the US would have been in the right to shoot down one of the buzzing Russian aircraft — signalling the incredible tensions facing this part of the world.