When we first moved in, all we had was our Aussie. She fell in once just after we got here. Then over the summer, she started hanging out in the water, but on the stairs (more of a "sunning ledge" I guess), but she refuses to actively swim in it. We have tried just taking her in the pool with us, but she immediately swims back to the ledge or the side stairs and gets out. Guess she just doesn't like it, but at least she knows how to get out. We don't use a solar blanket or anything, so I'm not worried about her. If she fell in, she'd just get back out. We also dogsit my father in law's dog and she LOVES swimming and will happily jump in and swim around and get out when she's ready.
However, we just got a goldendoodle puppy 2 weeks ago. Twice now - with us standing less than 15 feet away - he has fallen in because he's clumsy and, well, a dumb puppy. He immediately swims over to the edge, but he can't get out and since we haven't been swimming yet, he doesn't know where the stairs are. This has not given him any fear of the pool, but it does mean we have to be hyper vigilant when we have him outside. He absolutely IS NOT allowed out there alone because one, he puts everything in his mouth that he can and we don't want him eating the plants or rocks, and two, we don't want him falling in and drowning. Eventually he'll be fine, but he's not there yet.
My buddy has a middle-aged golden retriever, and he has full reign of the backyard at their house. If he's hot, he'll go out the back door and put himself in the pool - usually just laying down on the sunning ledge. All dogs are different I guess, but until you know how they deal with water, and until you're absolutely certain they know how to get out, you just have to play it very safe.