Most dogs love swimming and splashing. Labs and other retrievers seem born with an instinct to seek out places to get wet. But other dogs don't like water at all, may not have learned to swim and may not be comfortable on boats.
If your pooch falls into that category, it's best to introduce him safely and gradually to the water, and to outfit him with a flotation vest. The jacket could save his life in case he falls in, and it's also good insurance for dog-paddling in deep water. A brightly colored vest also helps you keep track of Fido while he's running around on shore. With that and a spot of sunscreen on his nose, you're good to go on a houseboating vacation.
Here's a fun "story in photos" that goes well with this theme of water safety for dogs . . .