Umm Khararim, the iconic 'St John's Caves', is a labyrinth of interconnected tunnels, caverns and swim-throughs where shafts of sunlight pierce narrow openings to create cathedral-like light beams. The maze of pristine coral passages and the dramatic illumination make it one of the most photogenic dives in the southern Red Sea. Most passages are shallow and well-lit, but a guide is essential to navigate the network.