Preheat the oven to 350 degrees F (175 degrees C).
Beat brown sugar, butter, and white sugar in a large bowl with an electric mixer until creamy. Beat in eggs, one at a time, until combined. Stir in peanut butter, water, and vanilla.
Combine flour and baking soda in a separate bowl. Stir dry ingredients into the wet ingredients until just combined. Stir in oats and chocolate chips. Drop by teaspoonfuls onto ungreased cookie sheets.
Bake in the preheated oven until lightly toasted on the edges, 8 to 10 minutes.
Remove from the oven and transfer to wire racks to cool.