What is the name of a large stream of moving water that flows in the ocean?

The term for a large stream of moving water that flows in the ocean is "current." Ocean currents are significant because they play a vital role in regulating global climate, transporting heat from the equator towards the poles and influencing weather patterns. They can be surface currents, which are driven by wind, or deep-water currents that are influenced by factors such as temperature and salinity variations, known as thermohaline circulation.

Other water bodies mentioned, like creeks and streams, refer to smaller bodies of freshwater flowing on land, which do not capture the scale or characteristics of ocean currents. An estuary is a transition zone where freshwater meets saltwater, typically at the mouth of a river, and is not a large moving body of water in the ocean itself. Thus, "current" is the most accurate and specific term for describing large movements of water in the ocean.