One thing we heard were visible from the beach were a number of stromatolites. According to Wikipedia "Stromatolites provide the most ancient records of life on Earth by fossil remains which date from more than 3.5 billion years ago". Apparently it's a pretty recent discovery that these buggers are still growing and not just rocks, and an even more recent realization that they have been sitting right in front of us in a number of places around the world, including the Exumas.
|Stromatolites as much as 3.5B years old|
|Stromatolites at Highborne Cay, Exuma|