This dungeon has no Heart Orbs, and no way to recover HP. This raises the dungeon difficulty significantly. You need to carefully consider your moves so that every round deals damage, and clear out enemies that are about to attack if possible.
There are 10 battles in this dungeon, so take care to prep your skills before the boss battle. Due to lack of recovery, try to stall on early weak monsters, and be sure to keep an eye on HP.
The final boss Blue Skydragon, Nirai Kanai attacks every two rounds. Since there are no Heart Orbs, there are two strategies: either kill it quick before it kills you, or wear it down with an auto-healer.
All enemies are water type in this dungeon, so wood-type team members will make it easier to clear mobs.
Dragon that specializes in ATK (highest in the game), but weak in other areas. Main skill is okay for clearing trash mobs, but impotent against high-defense bosses. Leader skill is not very useful due to many similar skills.
Sea Devil Kraken
Kraken has a special orb-enhancing skill that can further increase water type damage. Although its RCV is negative, water teams often have high RCV so there's not much need for concern.