A cool current is an ocean current with a water temperature lower than the surrounding sea. Most cool currents flow from high latitudes to mid-low latitudes and are characterised by low temperatures, low salt contents, high oxygen and nutrient contents and large amounts of plankton. When cold water flows through the warmer ocean, fog can easily form, causing navigation unsafe. In coastal areas where the cool currents flow past, water moves upward and brings nutrients to the surface. Because of their high oxygen contents, these areas are excellent breeding grounds for fish and marine life.