Ocean Water vs River Water: What's the Difference? Ocean water and river water differ mainly in salinity, movement, and ecological roles. Ocean water is salty, with a salinity of around 35 parts per thousand, and it covers most of Earth’s surface with deep, vast bodies of water. It's constantly in motion due to tides, waves, and currents, and supports marine life such as whales, coral reefs, and sharks. In contrast, river water is fresh and flows from higher ground toward oceans, usually carryin