Zostera is found on sandy substrates or in estuaries submerged or partially floating. Most Zostera are perennial. They have long, bright green, ribbon-like leaves, about 1 cm wide. Short stems grow up from extensive, white branching rhizomes. The flowers are enclosed in the sheaths of the leaf bases, the fruits are bladdery and can float.
Zostera beds are important for sediment deposition, substrate stabilization, as substrate for epiphytic algae and micro-invertebrates, and as nursery grounds for many species of economically important fish and shellfish. Zostera often beds in bay mud in the estuarine setting. It is an important food for Brent Geese and Wigeon.
The Slime mold Labyrinthula zosterae can cause wasting disease of Zostera, with Z. marina being particularly susceptible, causing a decrease in the populations of the fauna that depend on Zostera.
Eelgrass has been used for food by the Seri tribe of Native Americans on the coast of Sonora, Mexico. The rhizomes and leaf-bases of eelgrass were eaten fresh or dried into cakes for winter food; It was also used for smoking deer meat. The Seri language has many words related to eelgrass and eelgrass-harvesting. The month of April is called xnoois ihaat iizax, literally "the month when the eelgrass seed is mature".
Zostera has also been used as packing material and as stuffing for mattresses and cushions.
Eel grass once grew in abundance in Barnegat Bay, NJ, where it was dried out and used for house insulation (see the Governor's summer mansion in Island Beach state Park). Unfortunately, a blight wiped out the eel grass, which ended harvesting of the plant. The plant is making a gradual comeback.