Location: Isle d'Oriens -> scene with a candle chandelier Hint: Click everywhere you can. Notice how the monsters are water monsters... ;) That's the only hint allowed.

FIGHT!

After each battle, you will receive two options: Battle on! (Continue) | Escape before it's too late! (Return to the room that leads to Battle Chamber.)
(After each battle stage (3 battles long), you will receive a chest (Gold, Potion, or Rare Treasure Chest) and a "Stage (#) Complete!" message with two options: Battle on for more rewards! (Continue) | Escape before it's too late! (Return to the room that leads to Battle Chamber.))

Battles: Stage 1-3
Levels 1-20

• Blecch (1)
• Giant Piranha (25)
• Malgru (15)
• WhaleZard
• Young Water Dragon

Levels 21-40

• Blecch (1)
• Blecch (28)
• Braken
• Giant Piranha (50)
• Hydrak
• Malgru (15)
• Seadog
• TadZard
• WhaleZard
• Young Water Dragon

Levels 40+

• Blecch (28)
• Braken
• Drowned Angry Rat
• Giant Piranha (75)
• Hydrak
• Seadog
• Malgru (90)
• Water Dragon

Battles: Stage 4-6
Levels 1-20

• Giant Piranha (25)
• Malgru (15)
• Piranhas
• WhaleZard

Levels 21-40

• Blecch (28)
• Braken
• Gargel
• Giant Piranha (50)
• Hell Piranhas
• Hydrak

Levels 40+

• Braken
• Deadly Natator
• Gargel
• Giant Piranha (75)
• Hungry Braken
• Malgru (90)
• Sea Titan
• Water Dragon
• Serlissa the Water Dragon

Stage 6 Complete!
(Options: Okay-- who's in charge here?? (Continue) | Run away!!!! (Return to the room that leads to Battle Chamber.))

Battle: Boss Fight

• Phlox

(Receive a chest.)

Boss Defeated!

(Button) Water Battle Chamber completed!

(Return to the room that leads to Battle Chamber.)

Source

Pae, http://forums2.battleon.com/f/tm.asp?m=5934703