Azul marinho is a kind of fish stew made by caiçaras, or traditional southeast Brazil coastal populations. The name means, literally, "sea blue", the Brazilian term for navy blue.
The dish is made from fish slices and unripe bananas. The deep bluish hue results from an oxidation process during cooking.
When the dish is served, the bananas are mashed with the fish juices and cassava flour to form a pirão.
Several kinds of fish - grouper or namorado sandperch, for example - can be used to make azul marinho. A possible recipe would call for fish slices, pre-seasoned with lime juice, cilantro and salt. They would then be cooked with the unripe bananas, onions, tomatoes and olive oil. Some recipes call for unpeeled bananas to aid in the coloring. The fruit is peeled halfway through the cooking process.
Althouth the precise origin of the dish is obscure and it can be found on different areas of the Brazil coast, azul marinho is most popular on the São Paulo North Shore.