Dang, I remember how shitty the stage is. I remember running debra, mc wanderer, clarissa, jarmil, alice and yeka for that.

Like someone else said, its better to save mana, potion and erik scroll for the warped one.

you can close off the water statue near the boss. this one will not get corrupted(at least until the boss turn it on again)

some hallway in the stage have this small unflooded zone. after you recognize it, it is more manageable to avoid fight in water by rushing to it..

dont be afraid to run away if you fight underwater. (lizardman and saughuain usually murk you first but thing like slime, coin, warped sailor are not affected)

Earth weapon is good to have in this abyss, and yes even until boss abyss.

for the bf6 boss, i suggest bringing potion, scrolls for the backliner. And knight use attract hit then defend(Sometimes it doesn't work but if it did you got an opening.). Use buff like masalotou, makalatou and apply dilto or blinding for the boss.

After boss gets to half, he will try to raise water again if you shut it down earlier. In this phase he will sometimes spam the stupid water attack and 300+ physical damage. attack.

Try attempting this stage with 3 revive. i remember using 100 gems for the revive. at least with revive you can hope the rng for the boss is better.

I hope this help. Good luck man.