Preheat your oven to 350°F (175°C).
Combine the old-fashioned oats, brown sugar, all-purpose flour, baking soda, and salt in a mixing bowl and stir until well mixed.
Pour the melted butter and water into the dry mixture and stir until thoroughly combined.
Scoop out portions of the dough and form them into balls, placing them on the baking sheet with space in between.
Bake for about 12 to 15 minutes, or until the edges turn golden brown.
Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
