I responded in PM but will try to replicate my answer here for others intrested. 8)
Casey did a number on my old liner because she's a diver. She could pretty much be a certified diver if anyone needed a diving dog.

At the end of 06', she had 17 holes in my liner, most from 06' and some from 05' while going after diving rings and sticks or anything that would sink.
When I got my new pool in June 07', I banned all sinking toys and have not had to patch one hole and we're already heading into 2009. :-D Casey does scratch up the print liner on the walls when her ball gets near the sides because she pushes off of them. It is minor to me. I'd be more upset if she did rip a hole in the liner. (my old liner was a 20 mil, the new one is a 28 mil.) As far as getting out of the pool, she uses the steps. She usually flies through the air to get into it though.
I could never issue a swimming ban on her though, even if she did rip the liner because it's her pool!

I just take care of it. haha! When we suit up, she knows it's time to swim and she'll start this high pitched whine. It's so funny. My daughter says, But I don't wanna swim with Casey! I say, what makes you think she wants to swim with you?!

Stay out of the pool while she goes then! <preteens

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Point is, everyone swims and she has done very well since the new liner. I think it was more of training the kids that they can't use the sticks and rings anymore. We now use the remaining rings as dog toys. The dogs like to chew them and play tug-of-war with them in the back yard.
She will be sad when I take the pool down in a couple years but wait til she sees what I got commin!
