It has been my dream to swim with the dolphins. We passed on it both times were in Jamaica (the first time because it was a long drive ... the second time because our ride to the resort was so scary that I didn't want to leave the resort again until we absolutely had to). We also had the opportunity to be trainers for a day in Las Vegas, but decided not to (it was about $800 a person ... we could take another vacation for that cost!) - we just watched the dolphins instead in Last Vegas.
Cancun had several different locations to swim with the dolphins. The highly recommended one we chose not to do, because it included at 40 minute boat ride, and both Megan and I don't do great on boats out on the ocean.
The place we went to was great, and we were lucky - the group should have been ten people, but it ended up being just the four of us and one other person, so we basically got double time with the dolphins!
These animals are amazing, and it was so fun to interact with them! I won't share all 180 photos, but here's a few! :) Our kids have also LOVED the video that was taken of us. They watched it at least 30 times the first week!
We told our kids that someday they would get to do it too! (I think we better start saving money now ... ha!)