I dated a woman once who really liked these....
The seductive mermaid of lore has (inevitably) given its name to a cocktail especially suited to the world of beach, dock, patio, and surf. The beverage does not mix well, however, with the operation of a motorized vehicle, on land or in the water.
The mythic mermaid is equal parts woman and fish; her liquid equivalent contains equal portions of:
blue curaçao
vodka
orange juice and/or pineapple juice
grapefruit juice
and a twist of lemon or lime.
If you offer the Mermaid as a punch, you will naturally want to blend well. If you offer it in a glass to a friend, you may want to let the recipient stir, as the ingredients layer for an appealing visual effect.