Complex sentence: During the 17th and 18th centuries, the Cayman Islands became a stopping point for sea vessels sailing the Caribbean Sea in need of food; the turtles caught in the Caymans were taken aboard ship and kept alive as a source of fresh meat.
Split into simpler sentences: During the 17th and 18th centuries, the Cayman Islands became a stopping point for sea vessels sailing the Caribbean Sea in need of food. The turtles caught in the Caymans were taken aboard ship and kept alive as a source of fresh meat.