In recent years, researchers have identified a small group of stalactites that appear to have calcified underwater instead of in a dry cave. The “Hells Bells” in the El Zapote cave near Puerto Morelos on the Yucatán Peninsula are just such formations. A German-Mexican research team led by Prof. Dr Wolfgang Stinnesbeck from the Institute of Earth Sciences at Heidelberg University recently investigated how these bell-shaped, metre-long formations developed, assisted by bacteria and algae. The results of their research have been published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.