Some of the most common sea plants are seaweed, seagrass, marsh grasses and mangroves. Within each of these categories are a number of species, such as kelp, Sargasso grass, buttonwood, and red, black and white mangroves.
Bull kelp is the largest of the seaweeds. One of its largest habitats is along the Pacific Coast, with pockets of kelp stretching from Monterey Bay up to British Columbia. Attached to the ocean floor by a hold fast, a root-like structure, the flexible stem sometimes reaches 60 feet in length. Large air-filled bladders help hold the plant's leaves near the surface.
Seagrass and marsh grass are true plants. They have roots, leaves and propagate by producing flowers and seeds. Growing in shallow water, they are held in place by an extensive root system. Some of the plants in this category include paddle grass, star grass, turtle grass and shoal grass.
Mangroves are trees found in swamps and coastal areas, such as along parts of the Gulf Coast. They are adapted to survive in salt water, are evergreens and have an extensive root system that helps curb erosion.
Red mangroves live closest to the ocean or in salt-water bays. Black mangroves grow more inland, while white mangroves hug the shoreline, preferring shallower water than the red. Buttonwood, another species, prefers brackish shallow water, like that found where swamps and deltas empty into the sea.