These stromatolites at Hamelin Pool, Shark Bay, are living things and the longest living organisms on the planet. Stromatolite fossils are evidence of the earliest life on the earth, some dated at 3.5 billion years old.br/br/The water of Hamelin Bay is twice as saline as usual sea water because of a bar across the Bay's entrance and rapid evaporation from the shallow water. Most living animals, which feed on the bacteria and algae of which stromatolites are composed, cannot tolerate such saline conditions.