we did the dolphin encounter. DD#1 had a blast, DD#2 was a little more scared (she was 8 at the time) I thought it was a lot of fun. My only problem was I was very sick at the time, (food poisoning while still on land, long story!) so I wasn't completely 100% ok, but I still enjoyed it. If you're less adverturous, this is the excursion for you!
DD#1's friend went on the "Dolphin swim" and said that it was fun, but when they push you around, if you have a 2 piece swimsuit on, be very careful you might have to hold it up!
If you have seen the Mary-Kate and Ashley Olsen movie "Holiday in the Sun", the place that they had the encounter is this place.