There are various synonyms for the phrase "arm of the sea". These include: bay, cove, estuary, fjord, gulf, inlet, lagoon, loch, sound, strait, and tidal river. All of these terms refer to specific types of seawater formations that are generally surrounded by land on multiple sides and are connected to the ocean. Each of these synonyms may have slightly different connotations depending on their geography and context. For example, a bay might be a broad and shallow inlet, while a fjord is usually deep and narrow with steep cliffs on either side. Regardless of the term used, these bodies of water often provide important habitats for marine creatures and serve as valuable resources for humans.