Do all oceans and seas (not rivers or lakes) have the same level of saline (salt) concentration?
The bulk of the liquid water on Earth is contained in the vast oceans that cover more than seventy percent of the planet's surface. This water, unlike interior lakes and rivers, is saline water, or salt water; it contains a high concentration of sodium chloride, which makes it dangerous for most animals to drink, while other creatures such as fish and whales have adapted to live inside it. In general, ocean and sea water has a salinity of between 3.1% and 3.8% (Wikipedia), but this is dependent on several factors, including evaporation (which increases salinity) and flow from rivers (which decreases salinity). In areas with high precipitation, many river mouths, and low evaporation (meaning that the general humidity is high), the water will be of a lower salinity than in areas with high evaporation, low precipitation, and fewer river mouths. One of the lowest salinity bodies is the Black Sea, which has many rivers flowing into it; one of the highest salinity bodies is the Dead Sea, which is cut off from inflow, in a high temperature area, and has low precipitation.