I am aware that human lungs can't process water due to other reasons, but I am working on a setting that has genetically altered humans of various degrees and one of them can breathe water and air. I don't want them to have gills but rather just have lungs that can process water and air.
They would be;
- Salt water creatures
- Living in relatively shallow waters, maybe in extreme cases going down to 40 meters but almost exclusively residing at about 20 or less
- Possessing the same mental capability as humans
I know I would have to hand wave the details, but I just want to know that if the human lung could take oxygen from water if just making them stronger will work to keep the people from ripping open their lungs or passing out from straining to breathe. Would their lungs have to be bigger? Would they need a different cell structure?
Is this remotely possible or will I have to do as Star Wars does and just ignore the problems this would create?