I don't live aboard, but I do have four dogs that I take sailing regularly. They are border collies and love the boat.
I just wanted to warn you all that many of the "doggie lifejackets" being sold are worse than using no life jacket at all. If a dog were to go over, under, and pop back up in an upside-down position, some would make it impossible for the dog to right itself. They would float the dog on his back.
Also, a dogs head will drop under the water when it gets tired. If you lose your dog and go back to look for him, you may find him floating in his doggie PFD with his muzzle submerged - ie, dead.
I use human
life preservers placed upside down - on the dogs chest and stomach, with the strap going over his back. It allows the dog to float comfortably with his head rested on what would normally be the 'back collar' if on a human. It keeps the dogs head out of the water. In fact, with this arrangement, the dog can easily and comfortably swim in a normal doggie paddle position, as well as float safely while unconscious.
Yes, it would be better to use a good dedicated dog lifejacket in rough weather, however, a dog cannot swim with that sort of lifejacket on. If you're trying to have fuin with the dog, and keep him safe, he needs to be able to swim with the jacket on.
Many dogs drown near land because they simply get tired, and slide under, while no one is looking. I looked back once and noticed one of my dogs had slipped under. I ran back and had to pull her back up to the service. It can happen that fast. So I slap a lifejacket on the dogs every time I take them to the beach (morons laugh and yell "what's the matter, can't they swim?!")
With the lifejackets, the dogs can rest and float when tired, and have much more fun. When they see me taking out the jackets, they go wild.
With a human jacket, it must *not* have too much flotation, or the dog won't be able to right itself if it gets flipped upside down.