There are 25 Secret Seashells to be found in Link's Awakening. Once you have collected 20 of them to receive the Level 2 Sword. With this, you can shoot energy beams from the sword when you possess a full health meter.

Mabe Village 1. Go into the smaller of the two buildings in the screen with BowWow outside on a leash. Dig in the Southeast corner to reveal this seashell. 2. In the screen with a massive square area full of bushes, cut through them all until you reveal a secret seashell.   Tail Cave 3. There is a room in this dungeon with a crack in the west wall. Blow this up, and go inside to collect you seashell.   Mysterious Forest 4. There is a screen in the Mysterious Forest where a treasure chest is being guarded by a rock. Once you have the power bracelet, move the rock and open the treasure chest.   Ukuku Prairie 5. There is a small patch of of grass in one screen with four bushes around an empty square in the middle. Chop down one of the bushes, and dig in the centre square to reveal the seashell. 6. There is another screen with four bushes around an empty square of grass, this time its on the roof of the Key Shrine. Dig in the centre square to get the seashell. 7. Where there are all of those tire-looking rocks making up a sort of maze for you to go through, pick up the one which looks a bit odd on one of the corners. 8. One on screen there is a cave (you need to use a bomb to gain entry) which will take you up to an owl statue. Dig around him to get another seashell. 9. From the seashell shrine, go east and chop down the bushes you find.   Martha's Bay 10. Go to the north eastern corner of Martha's Bay, next to the sea. Chop down the lone bush there to reveal a hidden seashell.   Seashell Shrine 11 and 12. When you get 5 and 10 seashells, you can go to the shrine to collect two more.   Richard's Villa 13. In the secret passage, choose the left path to find a shell in a chest.   Martha's Bay 14. Find the Owl Statue and dig to the left of it to uncover a seashell.   Tree Telephone Booth 15. There's a telephone booth just to the right of a smaller tree. Charge this smaller tree and it will give out another seashell.   South of the Village 16. A tree here, on its own, will give you a seashell if you charge into it.   Yarna Desert 17. There is a path running down the far east of the desert. Follow the way to its top, and then walk down it to the very bottom to find a treasure chest with a seashell inside.   The Ghost's House 18. When the ghost tells you to look in his house, look under a pot to find the seashell.   Martha's Bay 19. In the screen with steps going into the river, and another smaller island in the river with steps going up to it, swim from one to the other and chop down the bush there.   Ukuku Prairie 20. There's a lone island in the water here. Slash the bush on it from the top. By now, you can go to the Seashell Shrine and claim your prize. However, if you feel like getting every seashell, continue:   Kanalet Castle 21. Use a chicken to float over the line pits just outside the castle grounds, and go down into the cave below via the stairs at the end to get your seashell.   Tal Tal Mountains 22. Go into the cave inside the mountains, and bomb the dry patch down there. Follow through the newly opened passage way and you'll be in a room with loads of treasure chests. The seashell is in one of these. 23. Go across the wooden bridge and at the end pick up the rock there to reveal yet another seashell.   Eagle's Tower 24. When you see a chest that looks impossible to get, go to the floor above and drop down through the floor so that you land under the chest.   Face Shrine 25. In the Face Shrine, look out for secret passages. There is one that will take you outside, onto an island in the middle of the rapids. Open the chest there for a seashell.