A pond is a body of water shallow enough to support rooted plants. Many times plants grow all the way across a shallow pond. Water temperature is fairly even from top to bottom and changes with air temperature. There is little wave action and the bottom is usually covered with mud. Plants can, and often do, grow along the pond edge. The amount of dissolved oxygen may vary greatly during a day. In really cold places, the entire pond can freeze solid.

Cattails are a familiar site in North America. Cattails are aquatic plants common in creeks, ditches, and ponds.

Water temperatures in lakes during summer months is not uniform from top to bottom. Three distinct layers develop: The top layer stays warm at around 65–75 degrees F (18.8–24.5 degrees C). The middle layer drops dramatically, usually to 45–65 degrees F (7.4–18.8 degrees C). The bottom layer is the coldest, staying at around 39–45 degrees F (4.0–7.4 degrees C). Since light does not penetrate to the bottom, photosynthesis is limited to the top layer. Because of the warmer waters and more plentiful food supply, almost all creatures spend the summer months in the upper layer.

During spring and fall the lake temperature is more uniform. Fish and other animals are found throughout the layers of the lake.

Even in cold climates, most lakes are large enough so that they don't freeze solid, unlike ponds. During the winter months some creatures hibernate in the bottom mud. Some fish continue to feed, but less actively. A layer of ice can develop on the top of lakes during winter. The ice blocks out sunlight and can prevent photosynthesis. Without photosynthesis, oxygen levels drop and some plants and animals may die. This is called "winterkill."

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