4. Cayman Trough, Caribbean Sea The Caribbean Sea has the world’s fourth-deepest point, Cayman Trough, at 22,788 feet below sea level. This trough is named for the nearby Cayman Islands and is situated between those islands and Jamaica. The Caribbean itself extends more than 1,000,000 square miles in an area bounded by South America, Central America, and the Greater Antilles. The Caribbean also has the world’s second-largest barrier reef, the Mesoamerican Barrier Reef. At 620 miles long, it trails only Australia’s Great Barrier Reef in length.

3. Java Trench, Indian Ocean The lowest point in the Indian Ocean, at 24,460 feet below sea level, is the Java Trench, also known as the Sunda Trench. This 2,000-mile-long trench is in the northeastern part of the Indian Ocean, near Java, Sumatra, the Andaman Islands, and the Lesser Sunda Islands. This trench was the site of one of the largest earthquake-tsunami combinations in recent memory, in 2004.

2. Puerto Rico Trench, Atlantic Ocean The Puerto Rico Trench, in the Atlantic Ocean on its boundary with the Caribbean Sea, extends 30,246 feet below sea level. The trench, named for the nearby country of Puerto Rico, is nearly 500 miles long. The trench has a history of large earthquake activity; the latest large quake was a 6.4, in 2014.