As a follow-up, I didn't want to infer that the areas won't be romantic. It's romantic to be in beautiful Hawai'i.
I'm a little concerned about your emphasis on swimming and snorkeling. There really isn't any safe and clean water swimming or snorkeling near Pahoa at all. All the calm water has bacterial issues. Kehena is a beach where people drown fairly often relative to other beaches on the island, and I would rate it barely safe for locals who know it really well, not safe for tourists.
On the west side, Hawi is 30-45 minutes to swimming and snorkeling. I would put that in the a bit farther out category rather than the lazing around where you're staying.
If you can't tell, your post makes me concerned about these choices given what you want to do. Vacation rental ads are the worst for making it seem like water is pristine that isn't, or swimmable when it's not.
Hawi is a great alternative experience to see a different side of Hawai'i, but not a very good place for water activities; you would do better in say Kohala Estates or that area if you want to swim a lot.