This is a comprehensive encyclopedia entry that contains information about marine ecosystems, ocean zones, ocean currents, marine resources, and environmental issues associated with oceans. Text for this entry is appropriate for the middle and high school grade levels.

This is an encyclopedia entry for the term "swamp," described as an area of land permanently saturated, or filled, with water. Text for this entry is appropriate for the middle and high school grade levels.

This encyclopedia entry is for the term "tide." The regular rise and fall of the ocean?s waters are known as tides. Along coasts, the water slowly rises up over the shore and then slowly falls back again. Text for this entry is appropriate for the middle and high school grade levels.