Cryptozoologist is a Story Mode achievement, and one of the ones Rockstar chose to hide, so Steam shows no requirement until you have already earned it. At 4.5% unlocked, it sits deep in ultra rare ground, well below most of the achievements tied to the main story missions. Rockstar hides a handful of Story Mode achievements this way rather than spelling out the trigger in advance, usually to avoid flagging a specific moment before players reach it naturally. Going by the low unlock number, this one looks tied to something well off the critical path, the kind of thing a player only finds by wandering rather than following mission markers in a straight line. There is no separate menu or tracker pointing at it. It simply appears once you cross whatever line Rockstar built into the game for it.
This is a hidden achievement. Play through the story and it will unlock at the right moment.
Achievements unlock on Steam, PlayStation (as trophies) and Xbox alike. Cheats disable them for the session, so play clean when you are chasing one.
The community companion for Grand Theft Auto VI. Database, maps, guides and tools for Vice City and the state of Leonida.