Topic: the finale.

Analysis: According to the meaning of the question, construct a right triangle and solve it with Pythagorean theorem.

Solution: according to the meaning of the question, let the water depth OB=x feet, then the withering length OA'=(x+ 1) feet.

According to the equation: x2+52=(x+ 1)2,

Solution: x= 12

So OA'= 13 feet.

So the answer is; 12, 13.

Comments: This question examines the correct application of Pythagorean theorem. Being good at observing the information of topics is the key to solving problems and learning mathematics well.