Skullfish & bombfish

Head north from Kakariko Village to the Bridge of Eldin. Just before you reach the arch of the bridge, turn left. A little bit past the bricks on the ground is another patch of brown dirt. Dig here to find the grotto. Then fish out the three skullfish and kill them, now you can catch the bombfish. Once you catched the bombfish you can add it to your bomb bag. But there are pretty tricky to catch!