For the first part of the battle, you’ll initially be fighting the boss’s two pincers. The pincers’ weak points are the eyeballs within. You’ll have to hit the eye at a certain angle when the pincer is open – the angle is pretty easy to guess at, and the game is rather generous with this.
If you notice a red eyeball at any point, back off or you’ll be hit with a tail sweep attack. Continue hitting the claws until both are destroyed. Additionally note that the boss may, with one pincer left, use its tail to hit you from above.
After destroying both pincers, the real fight begins. You’ll notice a third eyeball open up where, I guess, the boss’s head is. You can only hit this one with a thrust. After a few hits, the boss will dig into the sand.
Now, you’ll be able to note where the boss’s body is. Try to stay away from there, or you’ll be hit with its tail. Use the Gust Bellows to blow away the sand near the boss to eventually bring it aboveground again. Continue to thrust at its eye and later dig it up until it is defeated.