You might remember the sea monster you fought on the ship near the beginning of the game. It is possible to fight it again, but you need to know that it will be a lot stronger than before. It’s a good idea to have a Purikka Cobbler Salad on hand, as the extra health will certainly help in your survival. Another Support Spritnite that is a huge help is Water Shield, as it reduces some of the boss’ attacks to a much more manageable level. Lifeforce Logic is another good Support Spritnite for the added HP.
To begin the fight with this version of the boss, go to Serendale (probably around the time you get the airship) and cross the southern of the two bridges there. As you go east, you should see a dock that extends southward, which will have a NPC standing there, as well as a ship. Simply speak to him and you will start the battle.
BOSS - Schwarzstrom 2.0
Schwarzstrom will open up the battle almost as soon as it begins with Tsunami, which will likely deal around 400+ or so damage to everyone, so it’s possible that some lesser HP characters will die from this attack if you didn’t use a Purikka Cobbler Salad. Use your first turn with Setsuna (who should be in the party) to heal up with Cure II, provided she’s still alive, so if she died then you will have to revive her first.
Bellow is the same as last time, as it doesn’t deal damage and will stun your characters, emptying their ATB gauge. Water Spray only hits one character, although for good damage. Big Bite hits four times on one character, dealing about 80 or so damage for each hit. Bodyslam hits all characters for around 300 damage. The biggest threat is whenever the boss uses Dive, making it where you can’t do anything to it, and it is followed by Tidal Wave, dealing major damage (it’s stronger than Tsunami).
The basics of the fight involve being able to manage the boss’ attacks, mainly Tidal Wave, as if you can survive that, then you should be able to slowly whittle down its 11,000 HP. Bodyslam/Tsunami don’t seem to occur too much and most of its other attacks are single target. Setsuna’s Cure II, Luminaire (Momentum for Auto-Revive) and Inspire will go a long way, as will Endir’s Battlecry and Aura for back-up healing in case of emergencies. Your third member is up to you, but having Nidr for Blowbear will help a lot, as the boss is susceptible to both Stun and Confusion. Also, having Nidr’s Diffuse will be beneficial in using a single item on everyone.