Combining underwater exploration with innovative visualization, 'Drainage Ocean' reveals hidden evidence of underwater mysteries. It's not an artist's impression, but something that truly exists - until the last rivet. In the fourth season, it adopts a gripping new style, telling the story purely through the language of explorers and archaeologists, allowing the audience to stand by their side. The series includes... 1. Wild West 2. Battle of the Black Swan 3. Arctic War 4. Hollywood 5. The first batch of Americans 6. The Lost Empire of Venice 7. Mississippi River 8. Hurricane Revelation 9. The Great Barrier Reef 10. The Sea of Secrets