After resting they decided to go for a swim. The depth of the water is w times Dean's height. Dean is x feet taller than Ron. If Ron stands at y feet How deep was the water?
Let's denote Dean's height by $h_D$, Ron's height by $h_R$, and the depth of the water by $d$. 

Then we have $h_D = x + h_R$ and $d = w \cdot h_D$. 

Substituting the first equation into the second, we get $d = w \cdot (x + h_R)$. 

Now we know that Ron stands at $y$ feet, so $h_R = y$. 

Substituting this into the equation for $d$, we get $d = w \cdot (x + y)$. 

This is the final answer.