Put oatmeal and water in a pot and bring to a boil.
Once it starts boiling, reduce to medium heat and stir until the oatmeal softens.
Drain the oil from the canned tuna using a strainer.
When the porridge is done, add the tuna and mix well.
Season with salt and pepper to taste.
Serve in a bowl and, if desired, top with chopped scallions or sesame seeds.