In relation to Cravalgi (specifically ch 62-63)
I have not read anything past Vol. 14, so if this is explained in the other chapters then I guess tell me if I am wrong. It has also been a while since I read this and the proceeding volumes, so i might be forgetting something.
In chapter 62, when we first see him, it is stated that he has been dried out and that no creature has touched him; we even see that Faputa is scared. (I am going to assume that it would still take a while to completely dry out seeing as how the heat has not posed a major issue to any character yet.) Also in chapter 63 Cravalgi is called a "genius solo diver," and since one of the biggest obstacles of the abyss are the creatures within. It would be fare to assume that he does not have much issue dealing/avoiding with them. It is also heavily suggested that they are part of the "priestess's" party/group, as it is called in my translation. Now priest/priestess has a often has certain mystic adjacent connotation. Could he have a sort of "blessing" given by the priestess? One that would make the creatures of the abyss fearful of him and not approach, let alone attack him. If so it would make sense of his ability to solo dive and how nothing has eaten his corpse yet. Faputa is the only one affect by him and she is also the one closest to being an abyss creature (although she kind of is one strictly speaking.) Blessings are often spoken about in this series, and seeing as how the person called priestess has been around for quite some time in the deeper layers she could have access to a relic or power that would warrant the title.
Now I might be forgetting something from a later chapter that could change this or prove this wrong, so if there is let me know.