Let \( x \) be the total amount of time Kendall and her friends spent at Aqua World (in hours). According to the information provided, floating down the Lazy River for \( \frac{1}{2} \) hour is \( \frac{1}{4} \) of their total time.
We can set up the equation as follows:
\[ \frac{1}{4}x = \frac{1}{2} \]
Now, to solve for \( x \), we can multiply both sides by 4 to eliminate the fraction:
\[ x = 4 \times \frac{1}{2} \]
Calculating the right side:
\[ x = \frac{4}{2} = 2 \]
Thus, the total amount of time Kendall and her friends spent at Aqua World is \( 2 \) hours.