Shell Blade

Shell Blades are large, spiked, aggressive bivalve enemies that can be encountered both in the water and on land near water. While their shells are hard, their internal muscles are quite weak, and as such become vulnerable when their valves open.

The Legend of Zelda: Ocarina of Time
In The Legend of Zelda: Ocarina of Time, Shell Blades appear heavily in the Water Temple, and later make a small appearance in the Gerudo Training Ground. When Link approaches, they slowly turn their spiked hinges towards him and quickly skip in his direction. If he blocks or evades one, it turns toward him with its valve open briefly before attacking again. Underwater, they can only be attacked with the Hookshot or Longshot, but on land, other weapons like swords can be used, while weapons like bombs and the Megaton Hammer can bypass their defenses completely. In Master Quest, only one Shell Blade appears, being in the Gerudo Training Ground.

The Legend of Zelda: Majora's Mask
In The Legend of Zelda: Majora's Mask, Shell Blades look and act the same as before, but are only found underwater so only Zora Link can battle them effectively. They appear in the Pirates' Fortress where they re in some of the same tanks as the Zora eggs, and later appear in one room of the Great Bay Temple.

The Legend of Zelda: Twilight Princess
In The Legend of Zelda: Twilight Princess, Shell Blades appear in the Lakebed Temple, where they appear only underwater. They act similar to before, but are larger, slower, and more durable. Now, their spikes are located around their valves, which they slowly open before lunging forwards while chomping. Now, the sword can be used to attack them even while underwater, but it only effective when used horizontally. A few hits from it or the Clawshot severs the muscle, noticeably releasing a cloud of blood into the water.