Bring water and milk to a boil and stir in oats and salt. Reduce heat to medium-low and bring to a simmer. Cover pan and cook 20-25 minutes until oats are tender. Remove from heat and let sit for 2 minutes before serving.
Heat butter in a skillet over medium heat and place sliced bananas in a single layer in the butter. Cook until bananas are lightly browned on one side-- about 5 minutes and flip. Sprinkle brown sugar over bananas and continue to cook an additional 3-5 minutes or until remaining side is golden. Sprinkle 2 tbsp of water over the bananas and swirl pan to deglaze the hardened sugar.
Spoon oats into 4 bowls and top with bananas and additional milk if desired.