Have you ever had or known a dog that can't swim?

I had never really thought about it, but always assumed that dogs instinctively know how to swim. I have seen a lot of videos lately where owners are putting their dog in a life jacket when going near water. I’ve heard several owners say that they are taking their dog to the pool to teach it how to swim. On my Gramp’s farm, we NEVER had a pet dog; however, we did frequently find a bag full of puppies tossed out on the side of the road & they automatically became pets for the kids. Almost all the orphaned canines spent a good portion of their life swimming in the pond in the cows pasture. I don’t remember one ever drowning. I do realize that a dog can get in a situation where they get in trouble & grow so tired that they can no longer swim & might then drown. So, now I’m wondering, do we really need to teach our dogs how to swim or force them to wear a life jacket?