Soak the oatmeal in water for a while.
Soak the seaweed in water and cut it into bite-sized pieces.
Add water, soaked oatmeal, and seaweed to a pot and bring to a boil.
Once it boils, add tuna and soy sauce, and stir well.
Simmer on low heat for 5 more minutes.
Adjust the seasoning with salt at the end.