Final answer:
When snorkeling in the Bahamas, the tall rock formations under the water are likely stromatolites, which are layered sedimentary structures created by the activity of cyanobacteria.
Step-by-step explanation:
When snorkeling in the Bahamas and observing tall rock formations under the water, you are likely viewing stromatolites. These are sedimentary structures that are formed by the activity of prokaryotes, specifically cyanobacteria. Stromatolites represent some of the oldest evidence for life on Earth, and they are created by cyanobacteria trapping sediment and forming layered rock made of carbonate or silicate.
Although most stromatolites are found in the fossil record, there are still places in the world where these structures are actively forming. For example, growing stromatolites can be found in areas like Lake Thetis in Western Australia and the Anza-Borrego Desert State Park in California. The buinding of these layered formations is a slow process as cyanobacteria gather and bind the minerals precipitated out of water.