To find the radius of a circular swimming pool, you can use the formula:
\[ \text{Radius} = \frac{\text{Diameter}}{2} \]
Given that the diameter of the pool is 20 feet, the radius would be:
\[ \text{Radius} = \frac{20 \text{ feet}}{2} = 10 \text{ feet} \]
So, the radius of the swimming pool is 10 feet.