Lake Atitlán sits in Guatemala's highlands like a mirror of the sky, surrounded by three towering volcanoes and Mayan villages around its shores. Beneath the surface, the lake tells a story of fire and water colliding—jagged lava flows, sunken cliffs, and active thermal vents that still erupt from the lakebed. In some spots, the sand is so geothermally heated you can bury an egg and return the next day to find it cooked. Divers explore not only these vents but also the submerged ruins of villages lost when the lake rose unexpectedly decades ago.