Move an oven rack to the middle position and heat oven to 325°F.
Transfer crushed pineapple to a mesh strainer and drain well, saving the juice to drink if you wish.
Add the drained pineapple, cherry pie filling, whipped topping, marshmallows, and shredded coconut to a large bowl. Stir until mixed well. Cover bowl and place in fridge to chill while you're preparing the crust.
Place the broken graham wafers in the bowl of a food processor. Pulse the food processor until the wafers form uniform crumbs. Add the granulated sugar and melted butter and process until the mixture resembles wet sand, scraping down the sides of the bowl as needed.
Press the graham crumb mixture firmly into a 9x13" rectangular baking pan. Bake for about 15 minutes, until the crust is slightly browned at the edges, and smells toasted. Cool to room temperature.
Spread the cherry ambrosia mixture evenly over the graham crust. Cover with plastic wrap and place into the fridge to set, at least 1 hour. Cut into squares to serve. Serve chilled.
Notes
If you can't find a larger 20 ounce can of crushed pineapple (approximately 590mL), use two smaller cans (they're typically available in 398mL in Canada). Alternatively, use 2 cups of chopped fresh or frozen (thawed) pineapple, and pulse it in a food processor for a few seconds to resemble canned crushed pineapple. If you can only find larger containers of Cool Whip (often available in 1L containers in Canada), use only 1/2 of a tub.If you don't want to process your own graham wafer crumbs, you can also use packaged graham crumbs. Use 250g (9oz) or 2 1/2 cups of crumbs in this recipe. If you need your Ambrosia Squares to be gluten-free, be sure to buy gluten-free graham wafers or crumbs.