I have been there twice with a non-diving spouse. In fact, I have dived all over the world with a non-diving spouse. She loves to snorkel, and she will accompany me on boats when it makes sense to do so.
Note the phrase "when it makes sense to do so." She has done liveaboards with me in Australia and boat trips in Belize. She snorkeled the Blue Hole in Belize--the outer reef is beautiful. She did every boat trip we did in 3 weeks in Palau. She did the manta ray dive in Kona and had a great experience.
She did not, however, dive with me on Kauai. The snorkeling experiences there off of a boat were not good. If the features are too deep for good snorkeling, you are better off with the spouse snorkeling off a beach or on a special snorkeling boat rather than accompanying you on a boat and looking at water. When we were in Belize together, while I was diving on several days she booked a snorkel guide who gave her an outstanding experience that she still remembers fondly. After the Blue Hole trip in Belize, a guide took her on a great trip on Half Moon Caye.
There is no reason that a diver and a snorkeler can't have a great vacation together if they just understand that it does not always make sense for them to be together.