The nature of the dog is very important. I agree that a life jacket is mandatory for dogs. It is also a good idea to have a harness on them that can be used for lifting.
One time, when I had my dogs on the boat (two golden retrievers and a small black mutt who thinks she is a golden retriever), we were tied up at our slip and going into town. The Admiral took the dogs as I was closing up the boat. I came up out of the cabin to hear the Admiral saying, "It's OK, you're fine" and hearing splashing. I rushed over to the rail to see the Admiral holding the older golden by the collar as she was swimming next to the boat. I jumped out onto the slip and got my arms around her. I had to lift a wet, 75 pound dog out of the cold water. She was fine, never panicked, and happy to be in the water. The other dogs were watching and very concerned. In this case, a doggie PFD wasn't needed but a good harness would have helped me get her out of the water.
I later found out from the Admiral that when she jumped off the boat onto the dock, she slipped a little and her back feet hit the edge of the dock and she slid backwards into the water. Being a water dog, she was fine in the water and that made getting her out relatively easy.
"When in command, command." -- Admiral Nimitz
Difference between a power boater and a sailor out on the water: A power boater is going some place special, a sailor is already there.
s/v Zotz 1981 Pearson 365 Ketch Hull #375