NOAA Okeanos Explorer Program, Océano Profundo 2015: Exploring Puerto Rico’s Seamounts, Trenches, and Troughs Mona Passage is an almost entirely submerged section of the island arc and carbonate platform, with water depths generally between 100-700 meters, but as deep at 1,000 meters. The morphology of the seafloor in this region is composed of a mix of erosional, karst, depositional, and fault features, overprinted on the original layered fabric of the carbonate platform which is exposed almost everywhere across the passage.