Peter, I'm also not aware of any special impact of spouses on the general duty to care in negligence, but I have heard that some states have spousal relationships falling into a "special relationship" as regarding the duty to rescue. That of course still wouldn't affect the general negligence claim. But just as a special gift to Teamcasa, if you live in one of those states, you'll be happy to know that diving with your spouse may expose you to even more liability than if you were diving with a stranger
I think the point is that it would be sorta like suing yourself if all your assets are joint assets.