Seaweeds are any of a large number of marine benthic algae. They are macroscopic, multicellular, and macrothallic, in contrast with most other algae.

Seaweed is often found in the seashore biome - Source

Any large alga growing in the sea or on rocks below the high water mark; such plants collectively - Source

Seaweeds are extensively used as food by coastal people, particularly in East Asia, e.g. Japan, China, Korea, Taiwan, and Vietnam, but also in Indonesia, Peru, the Canadian Maritimes, Scandinavia, Ireland, Wales, Philippines, and Scotland, among other placesn the biomedicine and pharmaceutical industries, alginates are used in wound dressings, and production of dental moulds and have a host of other applications. In microbiology research, agar is extensively used as culture medium. Source 

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Seaweed: Seaweeds are any of a large number of marine plants and protists in the category of benthic algae. They are macroscopic and multicellular, in contrast with most other algae. Seaweeds are often found in the seashore biome.

The Seaweed Site: This site is a source of general information on all aspects of seaweeds. Seaweeds are marine algae: saltwater-dwelling, simple organisms that fall into the rather outdated category of plants.

Seaweed Basic Information: Seaweeds (kaiso) have been an important part of the Japanese diet for many centuries. Today, various types of seaweed are used extensively as soup stock, seasonings and other forms in daily Japanese cooking. The following are the three most commonly used types of seaweed:

Types of seaweed: Globally there are over 9,000 species of seaweed divided into three major type