These fish, their skin, or armors, had very strong defensive abilities, and were completely immune to Water-type attacks. Their blood was also a great supplement for those who cultivated Water-type techniques, even if it wasn't used in medicine. After eating their meat, it would make the cultivator's body stronger, and it could strengthen their tendons and bones. Their bones were one of the best materials for Water-type magic tools. Whether it was used to refine magic tools or to add other materials, it could play a very important role in Water-type magic tools.
However, there was no place for people to rest in gloomy oceanic trench. Therefore, they could only prepare a boat on the sea. Otherwise, they could only float in the sky, which would be very uncomfortable.
If you prepared a boat on the sea, you had to leave someone to look after the boat. Otherwise, once you went into the sea, your boat would disappear.
