It is a good thing that this part of the sea is not highly terrorized by the man-eating merpeople.
The last time they have been here was when they sail through a shipping vessel that used to transport magical items to different places.
It is also the same ship that acts as a medium to bring fresh blood as well as the returning students in Magus Academia.
They traveled for around three months or so that time, and on the very last day of their voyage to Magus Academia, they got attacked by the merpeople.
Many of the aspiring young warlocks and sorceresses met their demise at that time.
For they all fall under the charm of the merpeople and they were mercilessly dragged away by the vicious merfolk underwater. Probably ending up as one of their food supply.
Mu Lingxi and the two Long brothers traveled together on that same ship so they were aware of what happened to this place.