Rinse the oatmeal and seaweed thoroughly to prepare.
Soak dried seaweed in cold water, then squeeze out the excess water.
Drain the oil from the tuna using a strainer.
Add water and seaweed to a pot and bring to a boil.
Once it starts boiling, add the oatmeal and tuna.
Simmer and stir over medium-low heat for 5 minutes.
Season with salt to taste and serve.