A leaf floats on a pond. A ripple wave makes it bob up and down 18 times in 12 s…

Step 1. Frequency and period. $f = \dfrac{18}{12\ \text{s}} = 1.5\ \text{Hz}$, and $T = \dfrac{1}{1.5\ \text{Hz}} = 0.667\ \text{s}$.

Step 2. Speed. $v = f\lambda = 1.5\ \text{Hz} \times 0.090\ \text{m} = 0.135\ \text{m/s}$.

Step 3. To the frog. $t = \dfrac{1.35\ \text{m}}{0.135\ \text{m/s}} = 10\ \text{s}$.

Step 4. The leaf. No. The leaf moves up and down, and a little to and fro, about the same place. The ripples carry energy past it, not water or leaves.