Bake the Cake: Preheat oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan. In a large bowl, combine cake mix, eggs, milk, and oil. Beat with a mixer on medium speed for 2 minutes until smooth. Pour into prepared pan and bake 28–32 minutes, or until a toothpick inserted in the center comes out clean.
Prepare the Filling: While cake is still warm, poke holes all over the surface using a skewer or fork. In a bowl, whisk together cream of coconut and sweetened condensed milk until smooth. Pour evenly over the warm cake, allowing it to soak into the holes.
Cool and Top: Let the cake cool completely. Spread thawed whipped topping evenly over the surface. Sprinkle shredded coconut generously on top.
Chill Before Serving: Refrigerate for at least 2 hours (or overnight) before serving to let the flavors meld together.
Serving and Storage Tips
