To find the circumference of a circle, you can use the formula:
\[ C = \pi \times d \]
where \( C \) is the circumference and \( d \) is the diameter of the circle. Given that the diameter is 18 feet and using \( \pi \approx 3.14 \):
\[ C = 3.14 \times 18 \]
Now, calculate:
\[ C = 3.14 \times 18 = 56.52 \]
Rounding to the nearest foot, the circumference is:
\[ \text{C} \approx 57 \]
So the circumference of the swimming pool is 57.