According to the Wiki, squid should spawn in any biome at any depth. However, no matter how massive of a squid spawning area I create, I cannot get a squid to spawn anywhere except my AFK fish farm. This is in a Deep Ocean biome in a drought custom world, although neither of those should affect anything to my knowledge. Also, if any information is missing or extra, please tell me, as I just started reporting the many bugs I have found.