This body of water borders Eastern North America, the Caribbean nations, and the continent of South America. Explorers, settlers, and slaves crossed this body of water to reach the Americas.

Atlantic Ocean

Explanation:

ATLANTIC OCEAN is the body of water that borders Eastern North America, the Caribbean nations, and the continent of South America. It is also the body of water that Explorers, settlers, and slaves crossed to reach the Americas.

This is evident in the fact that the Atlantic Ocean is the body of water that separated the whole of the American continent both south and north of the continent, to the East from the European and African continent.