The deep water area between Valinokkam and Kilakkarai in Tamil Nady coast covering an area of 200 sq.km. was surveyed for the distribution of marine algae and seagrasses during January 1989. Totally 33 species of marine algae were recorded of which 8 species belonged to Chlorophyta, 8 to Phaeophyta and 17 to Rhodophyta. Only one species of seagrass Halophila ovalis occurred in the whole area surveyed. The vertical distribution of seaweeds and their abundance were investigated. Hydrological data collected from the area surveyed are presented.