This video from Facts in Motion illustrates how the sex of crocodiles is determined by environment and not genetics. The sex ratio of developing crocodile eggs is shown to be a function of temperature, thought to be mediated by a thermosensor protein. Climate change may impact or even cause the extinction of crocodile populations.
This sex-determination system is not so “unusual” because it occurs in other reptiles and fish species. But it is certainly interesting and gathering attention. The College Board’s 2018 AP Biology exam had a free response question about temperature-dependent sex determination in fish.