We did the sting ray excursion last month in Grand Cayman, had a great time. When you first get in the water, everyone is screaming because of the unknown. I did the same thing, but my husband said, "This is your excursion, you're staying in here" -- too funny. Then you just end up laughing and having a lot of fun. We had several younger kids in our group, too.
Go, have fun, we sure did.