Stir gingersnaps, coconut and macadamia nuts together in a bowl.
In a separate bowl, stir sweetened condensed milk and rum extract together.
Place pineapple in 9x13 pan.
Pour half of sweetened condensed milk over the top of pineapple.
Top with all of the cookie/coconut/macadamia nuts.
Pour remaining sweetened condensed milk over the top of crumbs and pineapple.
Bake at 325 for 20-30 minutes or till hot and bubbly. Cover with foil part way through if it's getting too brown.