1) Preheat oven to temperature of 200 degrees.
2) Add just enough olive oil to an ovenproof pan to cover its surface.
3) Add the aubergine and marrow, followed by the potatoes and tomatoes.
4) Add 1 tablespoon of tomato puree on top and then sprinkle with salt, pepper and oregano.
5) Top with some more olive oil and then add the water.
6) Use your hands to toss the ingredients around.
7) Bake in the preheated oven for about 15 minutes.
8) Remove the preparation from the oven and use a wooden spoon to give a good mix to the ingredients and move then around.
9) Put the briam back in the oven and let it cook for about 1 1/2 hours more.
10) Take the preparation out of the oven, transfer to a serving plate and serve while still hot.