Difficulty in Believing in the Exchange of the Devil Fish
It is indeed challenging for those who have not witnessed the exchange of the devil fish to believe in such an occurrence. There are several reasons why this may be the case.

Lack of Evidence
One of the primary reasons for disbelief is the lack of concrete evidence. Without any visual proof or firsthand accounts, it is natural for people to be skeptical about the exchange of the devil fish.

Unusual Nature of the Exchange
The concept of exchanging a devil fish for anything may seem unusual and fantastical to many. The idea of such a transaction goes against our understanding of the natural world and may be difficult for some to accept.

Cultural Differences
Cultural differences can also play a role in shaping beliefs about the exchange of the devil fish. In some cultures, such exchanges may be more accepted or even considered commonplace, while in others, they may be viewed with skepticism or disbelief.

Limited Exposure
For those who have not been exposed to stories or traditions involving the exchange of the devil fish, the concept may be entirely foreign and therefore difficult to believe. Without prior knowledge or context, it can be challenging to wrap one's head around such a concept.
In conclusion, the exchange of the devil fish is a phenomenon that may be met with skepticism by those who have not witnessed it firsthand or been exposed to the cultural beliefs surrounding it. Without concrete evidence or personal experience, it is understandable why some may find it difficult to believe in such an occurrence.