Tides Tides are the up and down (vertical) movements of water with respect to the land. Tides are produced by the gravitational pull of the moon and the sun.
	Currents Currents are the back and forth (horizontal) movements of the water.  Currents are caused by many different things including the tides, winds and freshwater runoff.
	Sea Water Temperature We also measure sea water temperature. Sea water heats up and cools down much slower than air.
	Salinity The amount of salt in water is called salinity. Freshwater has a salinity of 0 and sea water at the ocean is around 35 PSU.  35 PSU means that there is 35 grams of salt for every kilogram of water.  The salinity in the ocean can be different from the top of the water to the bottom!
	More information on our Oceans and Coasts Find information about fish, marine mammals, our coasts, navigation and the many facets of the waters that surround our nation. For more information about tides and currents click here.

Adapted for CO-OPS from a Publication of the NOAA Education Team.

 Last Updated: 04/27/00