After resting they decided to go for a swim. The depth of the water is 15 times Dean's height. Dean is 4 feet taller than Ron. If Ron stands at 13 feet how deep was the water?
First, we know that Dean is 4 feet taller than Ron. So Dean is 4 + 13 = 17 feet tall. 
Then, we know that the depth of the water is 15 times Dean's height, so the depth of the water is 15 * 17 = 255 feet.