Good luck to your fiance!
I had a similar experience. I also learned to dive because my boyfriend loves diving, and he wanted me to try diving. First, I had to relearn how to swim : ) . Learned swimming in grad school, then never swam. My boyfriend brought me to his LDS pool one afternoon a week for 4 months until I could pass the swim test. Then his friend, a dive instructor gave me one to one lessons.
I love diving! My boyfriend was very supportive, never pushy. He only wanted me to try it, and always said he would not be upset if I decided I didn't like it. My first few times out in OW were for me a little unnerving because I don't like water in my ears. Took me about 20 minutes to descend on my first dive, basically clung to a rock because I took my time descending. My boyfriend (also a DM) and the instructor were very patient. A group class would probably not have worked for me and I am lucky to have had the personal instruction.
Diving has brought us closer together as a couple. We are going to Curacao in March, our second dive trip together : )
Support and encouragement from the local LDS were very helpful as well.
M.