An arena first introduced in Monster Hunter Tri. This arena is fought completely underwater. Players can resupply oxygen by swimming through underwater air bubbles located in the center or swim to the surface to catch some air. This version of the arena also has a Dragonator, which you can use in various online event quests, such as Sea Power. Below the main entrance for large monsters there is a gathering point that you can gather life powders from. There are also two more gathering points. One contains two EZ Flash Bombs and the other one contains two Mega Potions.