You're asking what is the compensation for loss of use? You could get 100 lawyers and all would come up with different numbers. I would take the (distance to the Y * federal mileage rate) + (minimum wage * time to Y) + (fuel costs) as your true and accurate out-of-pocket losses.
All that said, I agree that this doesn't look like a pool ruined by one action of the pool guy on his first visit. This looks like a seam failure that was MAYBE contributed by some weight on one side of the seam and improper backer on the back.