The town of Ermina turns out to be a city for fish, where the whole town is submerged in water during high tide. The moment the party mentions Water God Dragon, the fish turn hostile.
That was a potion to help non-fish 
acclimate to the underwater environment.
Dieser Trank bewirkt,
Es una medicina para adaptar
al agua a los que no son peces.
Era uma poção para ajudar os não-peixes
a se acostumarem com o ambiente submarino.