Balahara

The soft mouth of Balahara is a weak spot. Strike it right after the monster spits mucus, while that opening is exposed. While Balahara is under the sand, its hearing is sharp. Keep an eye on that moment, and use a Screamer Pod obtained from Baunos. The pod forces Balahara up out of the sand. Knowing when the mouth can be struck, and when a Screamer Pod will draw the monster from below, is key.