The bottom of a river or stream where the water usually flows.
Streambeds are important for the health of the river and the creatures that live in it.
Examples:
The fish swim in the streambeds.
The rocks in the streambeds are very smooth.
The water flows over the streambeds.
The streambeds are like a busy city for the fish.
The streambeds are the highways for the water animals.
The streambeds are the homes for many small creatures.