Carved into a reef, 8km north of Dahab, is Egypt’s most infamous dive site. The Blue Hole is a gaping sinkhole that drops straight down – some say as deep as 130m. Exploring the deeper depths should be left to experienced technical divers, but there's plenty to discover close to the surface. The outer lip is full of marine life and a reasonable plunge into the hole is somewhat akin to skydiving. Depth: 7m to 27m. Rating: intermediate to advanced. Access: shore.