We did, for almost two years. She fell overboard several times, actually, but she just swam around to the back of the boat and climbed up the swim ladder. I actually have video of it, because once we purposefully dropped her in the water to make sure she could get back on.

She was a rescue, our daughter's boyfriend (who lived on the boat with us for a while) found her as a tiny kitten in a parking lot and managed to save her before she got hit.