I made this whole amethyst-ified coast trying to get them to spawn, but all I could get were Stone coloured ones. Surely they're not meant to be this rare? I've been hunting for one for over an hour! I'm gonna just spawn one in, but maybe the spawning mechanics/requirements need tweaking?

I'm playing 1.20.1, large biomes world on a server with this version installed: fish_of_thieves-mc1.20.1-v3.0.4-fabric

Hey I've improved Islehopper spawning logic a little bit. Now it can be spawned anywhere in the overworld. With only 2 requirements
1 - Spawning at coast
2 - Y Coord is less than or equals zero

Amethyst Islehopper you don't need to fill your ocean into amethyst land lol, just few of them like this image.

I will release a new version later.