We have been to Aruba 5 times and think that the best day experience you can have that will include snorkelling,open bar,good food(all inclusive) is at De palm Island.
We take our friends there for the day when travel to Aruba and all of them love the experience.
This is a great chance to go while you're on the cruise because you are probably going to be there until midnight or so which will allow you to go into town for the evening to shop and look around.
The cost of this excursion will be approx
60$ per person and includes everything.
Take a taxi to De Palm Island around 9 am
and you will get a short ferry ride (included in the price) to the island and you can stay there all day and eat, drink
and see some amazing fish that will blow you away.
You can probably book the excursion on line through the cruise ship web site but you may only get a half day for about the same price.
Have a great vacation.