Instructions
Open the chest near the entrance, then go all the way to the first intersection to make a right. After defeating some Medusas, open the chests for more items. Go left to beat some Hermit Crab Poos, and then head northward.
Beat the Cutlass Fish with 200 life points and go right at the next intersection. Open the chest, then go back to the main passage and head north.
Turn left at the intersection and beat the Broadsword Fish with shadow magic. Open the chest at the dead end, then go back to the main passage to turn right.
Remember the chest at the next intersection --- you'll need to open it later. Head north toward the cliff and defeat the monster for a chest to appear. Take the fish key from the chest and go back to the chest at the last intersection. Open it with the key.
Open the chest and take the Hexagonal Crystal. Use it on the shell back at the cliff, allowing yourself to cross the water.
Go straight to the checkpoint, where you'll find the Flara spell to the right. Go through the checkpoint.
Defeat the Hydrattler boss. Have two characters cast the Ground spell every round, and have the other two heal your party. Cure poisoned characters after battle, open the chests and continue on to head out of the cave.