Make The Vanilla Wafer "Sand": Add the vanilla wafers to the Ziploc bag. Roll over them with the rolling pin until they are thoroughly crushed. Or (if you prefer) you can also chop them using a knife. Set aside.
Cool The Alcohol: Pour the rum into the 2-cup measuring cup (or small bowl). Fill the the measuring cup with ice to make 1 1/4 cups. Set aside
Make The Jello "Water": Pour the jello crystals into a bowl. Boil some water in the kettle. Add 3/4 cup of the boiling water to the jello crystals and stir until dissolved. Add the rum and ice mixture. Stir until the water has thickened (which should take a minute or two). Remove any left over ice cubes. Then refrigerate in the bowl for 15 or 20 minutes (The mixture should be gelled but not firmly set). Stir the jello to give it the appearance of running water.
Put The Jello Shots Together: Spread a thin layer of crushed vanilla wafers over the bottom of each of the jello shot cups. Spoon some of the jello into each of the jello shot cups.Refrigerate the jello shots until firm (usually 3 to 4 hours). Just before serving, push the tail of the Swedish fish into each of the jello cups.
Very Important Tip: The Swedish fish will get slimy and mushy if they are left in the jello too long, so you will need to either add them to the jello shots just before the party starts, or make your jello shots the day you are serving them.
Spreading out your jello shot cups on a cookie sheet catches any spills that might happen while you are putting them together and makes them easy to put away in the refrigerator