They're good swimmers. Way back when, when I hunted 'coon, one led one of my dogs into a pond, waited till she was in the middle of it, and then jumped on the her head and drowned her. It was a shame, she was a very good hound; a blue tick.
Many people something in the pool that small animals can get on and use to get out of the pool. I think there are even some products sold specifically for that purpose that include a ramp for the animal to climb out of the pool on.
Edit: Here's the Skamper Ramp. Looks like it's a little under $50.00 from various online retailers. I'm sure there are other similar products.
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