If we could switch off all the genes in adult human stem cells AND identify and cut out the genes in fish that code for gills, we could perhaps insert the gill genes into the stem cell. We could then grow the gill tissue and implant it into a human - but the surgery to link the gills to the circulatory system would be a problem too. Also, how big would the gills have to be to allow a human (big) to get enough oxygen to survive in water like a fish (smaller)?
It would be so cool if we could do that. Then I wouldn't have to worry about holding my breath under water.. I do wished that we could do.. What if we turned into fish? We would be weird looking fish. But i'm still happy the way i'am, but i'm not when i go to the oceana and lakes to go swimming.....