My SO doesn't dive and probably never will.
When we go on vacation abroad, we find a compromise: She spends time tanning (which I thoroughly don't enjoy) and/or bathing at the beach or on the boat, while I dive. And we also do stuff together, so it's more a "vacation with some diving" than a "diving vacation".
Locally, we go out in the boat together. Sometimes she tends the boat while I dive, othertimes we just go boating and/or fishing.
I also dive with my local club and go on day trips or weekend trips with them. She stays home and does her things (whatever that is).
The only thing which is off the table is liveaboards. They're expensive, she doesn't belong there, and we don't have enough disposable income for three vacations (one for us, one for me and one for her) every year.
People in a relationship don't have to share all interests. They often don't. What's important is to find a compromise which works for all parties, respecting each other and each other's interests.