Charles Darwin, best known for his theory of evolution, made many significant contributions to the early study of marine biology. He spent much of his time from 1831 to 1836 on the voyage of HMS "Beagle" collecting and studying specimens from a variety of marine organisms. It was also on this expedition where Darwin began to study coral reefs and their formation. He came up with the theory that the overall growth of corals is a balance between the growth of corals upward and the sinking of the sea floor. He then came up with the idea that wherever coral atolls would be found, the central island where the coral had started to grow would be gradually subsiding