Thalassia is a marine seagrass genus comprising two known species.
Thalassia hemprichii (Ehrenb.) Asch. - Pacific Turtlegrass (shores of the Western and Central Indo-Pacific)
Thalassia testudinum (Banks ex K.D.König) - Caribbean Turtlegrass (Gulf of Mexico, Caribbean Sea, and Bermuda)
Media related to Thalassia at Wikimedia Commons
Data related to Thalassia at Wikispecies
Images of Thalassia at Algaebase