Why do rivers flow to the sea?
For grown-ups: the science
Rivers flow to the sea because gravity pulls water downhill through low places in the land.
Rivers flow from higher elevations to lower elevations because gravity drives water downhill. Channels form and change as flowing water erodes land and carries sediment; rivers may end in lakes, inland basins, wetlands, or the ocean, depending on the drainage basin.
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Transcript
A river wiggles across the land. Why does it keep going toward the sea?
Rain and melting snow collect in little streams high on hills and mountains. Water starts where the land is often higher.
Gravity pulls water downhill, so small streams join into bigger rivers. The water follows low places in the land.
Rivers carry the water downhill until they reach a lake, another river, or the sea. The sea is a very low, wide place for water.
So rivers flow toward the sea because gravity pulls water downhill. The land helps show water which way to go.