Heat olive oil in a meenchatti, add mustard and fenugreek seeds.
As they splutter, add onions and sauté the onions till they turn golden brown. Then add finely sliced garlic and cook for 2 minutes.
Add red chilli water to the sautéed onions and continue to cook till the oil separates from water.
Add water, kokum, fish, curry leaves, salt and garlic to make the curry.
Bring the curry to a boil and let it simmer for 5-6 minutes till the fish is tender.
Serve hot with boiled rice.