Habitat: A tolerant species that grows from the intertidal down to at least 50m. Often found growing at the shallow and/or deep extreme of continuous meadows of larger species. It is common in ground swell area and in the zone of medium depth, between 18 and 20 feet. This species usually starts to be present at a depth of 6 meters, where the seagrass T.testudinum zone ends. Distribution: The distribution of this species extends from Oceania and the Caribbean Sea, to the coasts of the Atlantic Ocean in Brazil. Depth: 0 - 50m Characteristics: Plants delicate and inconspicuous (up to 4 cm), though often forming dense monospecific stands. Oblanceolate leaves arise in opposite pairs at each node of the rhizome. Roots are formed opposite shoots, 1 per node. Fruits are spherical. Notes: Distinguished from mophologically similar H. johnsonii by the presence of lateral leaf spines. However, because H. johnsonii is thought to only exist in Eastern Florida, the only other species of Halophila in the area is likely H. baillonis which is larger and whose leaves are arranged in conspicuous whorls.