I was having the same problem, also took a cruise and had this drink, and have been looking for the recipe ever since. I was hoping someone would answer you request. When Andy suggested calling Royal Caribbean, I gave it a shot, but the lady I spoke to couldnt help me. She did say their webpage is scheduled to have a page listing their drinks sometime in 2007. I kept searching and found a link to Cruise letters and found another person asking the same question. Here was the response:

Delvin Litchmore, beverage supervisor with Royal Caribbean, shares the secret.

MANGO TANGO

1st part of drink:
1 oz. dark rum
1 oz. coconut cream
1 oz. pineapple juice

Blend with crushed ice.

2nd part of drink:
1 oz. dark rum
1 1/2 oz. mango concentrate
1/2 oz. orange juice

Blend with crushed ice.

Drink must must be layered in two, garnished with orange and cherry, and served in a 14-oz. Collins glass. (But I remembered the waiter adding a shot of dark rum on the top after he served it)
Good Luck,