1 can of cream of coconut (NOT COCONUT MILK. Cream of coconut is sweetened and thicker. A common brand is Coco Lopez. It's usually in the "ethnic foods" area, and bigger/nicer liquor stores usually have it.)
1 can of crushed pineapple, not drained
Liquefy the above in your blender, then add
3-4 c. of pineapple juice (I used a little over half of one of those big cans)
2-3 c. of coconut rum (Malibu, etc.)
I also added a big splash (~1 cup) of Sprite, as I was serving this in a punchbowl and wanted it to be thinner. I took rings of pineapple and froze them on a cookie sheet and floated them in the punch for ice cubes.
This drink can be dangerous as you can't taste the booze at all!