How to Create a drowning trap for a creature spawner in Minecraft

So during your time creating mines and exploring various cave systems you probably have discovered a few hidden coves with strange flaming cages in them. Those are creature spawners, they create zombies, skeletons, creepers and more. If you destroy it they stop coming out, but, if you leave it alone, they continue to spawn, now wouldn't it be great if you could create a way of being able to harvest the loot drops from them with little to no effort? Check out this video, in it, you will learn how to create a trap system around the spawner that drowns the enemies and then drags their items down into a square for collection.