In this question, we need to determine the pair of Island and Sea/Ocean that is not correctly matched.

Option 1: Cyprus in the Mediterranean Sea. This is a valid pairing because the island of Cyprus is indeed located in the Mediterranean Sea.

Option 2: Falkland in the Atlantic Ocean. This is also a valid pairing because the Falkland Islands are located in the South Atlantic Ocean.

Option 3: Chagos in the North Pacific Ocean. This is the incorrect pairing. The Chagos Archipelago is actually located in the Indian Ocean, not the North Pacific Ocean. Therefore, option 3 is the correct answer.

Option 4: Islas Cocos in the Indian Ocean. This is a valid pairing because the Cocos (Keeling) Islands are indeed located in the Indian Ocean.

In summary, the pair of Chagos and North Pacific Ocean is not correctly matched, making option 3 the correct answer.