Eelgrass, the name of two kinds of unrelated plants that grow underwater. The more familiar kind, also called tape grass and wild celery, grows submerged in spring-fed lakes from Nova Scotia west to North Dakota and south to Florida. The second kind grows in salt water along the North Atlantic coast. Both have slender vertical leaves that look something like small eels.

Tape grass has separate male and female plants. Male flowers break open and shed pollen on the water's surface. At the same time, rapidly growing stems push female flowers to the surface. After fertilization the plant coils spirally back below the water's surface, where the berrylike fruit develops. Fruit, buds, and leaves are eaten by ducks, geese, and turtles.

Tape grass makes up the genus Vallisneria of the family Hydrocharitaceae. Salt-water eelgrass is Zostera marina of the family Zosteraceae.