Add the flour, grated butter, and cheese to a large bowl, mixing until combined. Transfer the cheese mixture to a food processor and pulse until you have coarse crumbs.
Pulse in the water 1 tablespoon at a time until the dough forms a cohesive ball. Mold the dough into a disc shape, wrap it up in plastic wrap, and chill for at least 20 minutes.
Use your goldfish cutter to cut out as many goldfish as you can. Roll out the excess dough and cut some more until you've used it all. Place crackers on a parchment-lined baking sheet.