Alice,
If I remember correctly, that swim lasted about 1 1/2 hours including the instructions and video at the beginning.
There is an entrance fee to the park so be prepared. I think it was $10.00 per person.
This is something you will never forget. Book the earliest one you can get, so you can get back for the wedding. When we walked out of the park, there were cabs waiting to take people back to the ship. We were running late and we asked him to get us there quick......I don't think he used the brakes till he got there!
But we made it!
Allow yourself 2 hours to be safe. If you can book a 10 o'clock time, you will have plenty of time to get back to the ship, get showered and ready for that wedding.
I hope you have as great a time as Lisa and I did!