Seawater refers to water that is found in oceans, seas and other large bodies of saltwater. It contains various minerals such as sodium chloride (table salt), magnesium, calcium, potassium, and sulfate ions among others. The concentration of these salts varies depending on the location but typically ranges from about 3% to 4%. Seawater is also known for its high density due to the presence of salt which makes it heavier than freshwater.