Indonesia’s Bajau people, who for generations have spent the majority of their days diving and hunting underwater, have genetic adaptations that include spleens that are around 50% larger than those of their land-based neighbors. https://www.sciencemag.org/news/2018/04/indonesian-divers-ha...

You also have some populations who have been living in high altitude for many generations that have genetic adatptions to low-oxygen environments. https://www.sciencemag.org/news/2014/07/tibetans-inherited-h...