PARALLEL EVOLUTION OF SEAGRASSES. “Phylogenetic analysis of members of the entire order, based on the plastid gene encoding for RuBisCO large subunit, indicates that the return into the sea occurred at least three times independently through parallel evolution from a common aquatic-freshwater ancestor of terrestrial origin.”
http://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-11-8