You're at a dog park... and for some reason, a dog is way out on a frozen body of water.... it seems safe maybe, but do you let him keep running around?
When one dog fell in, a woman who is not the owner of the dog, got into the water and broke the ice to make a path to the dog and then bring him to safety. Everyone cheered them on [although the owner sounds like they have far less anxiety about the situation than I would].
In the end, they're all okay- the dog was running around a short time later [probably back on the ice, tbh] and the woman was in a warm bath.