Bottlenose dolphins may consciously vary their heart rates depending on how far they want to dive, in an effort to avoid decompression sickness
Source:
https://www.newscientist.com/article/2260624-bottlenose-dolphins-may-control-their-heart-rates-to-avoid-the-bends/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home