The following discussion is purely theoretical. At present, there is no mature, feasible and widely recognized method in the field of science and ethics to achieve the goal of giving the characteristics of non-human species such as fish (such as the ability to breathe underwater) to humans through gene editing. This kind of concept involves extremely complex biological, technical and ethical issues. The following introduces some key points involved in theory, but it does not mean that such a research direction has practical feasibility or legitimacy. [1. Theoretical basis and differences in gene function] · The characteristics of each species are the result of long-term evolution and environmental adaptation. The ability of fish to breathe underwater mainly depends on gills and their related cell structures and physiological mechanisms, while humans have established a gas exchange system based on lungs after a long process of mammalian evolution. · To transfer the underwater breathing ability of fish to humans, we must first clarify the key genes, regulatory networks and synergies with other organ systems (such as the circulatory system) that control the formation and function of gills. In contrast, the human genome lacks a directly corresponding "gill development" program. 【2. Current status of gene editing technology】 · Existing gene editing tools (such as CRISPR/Cas9) are mainly used to repair single or a few pathogenic mutations, while organ-level structural reconstruction and cross-species gene integration are far beyond the safety and controllability of current technology. · Even if it is theoretically possible to express fish-specific functional proteins in the human body, how to express them in the correct time and space and how to construct organ structures that work in coordination with other human systems are extremely complex problems. 【3. Biosafety and ethical issues】 · In terms of human gene editing, the international community has reached a broad consensus that genetic modification that affects future generations must not be carried out for non-therapeutic purposes. Introducing complex biological characteristics of non-humans into the human body may bring unknown physiological risks and serious safety hazards. · In addition, research involving cross-species gene manipulation may cause ethical controversy and must undergo extremely strict regulatory review procedures. At present, most countries and research institutions will be cautious or even prohibit such research. 【4. Scientific and technological challenges】 · Even if candidate genes that regulate gill development can be identified, their expression in the human body must be coordinated with the existing developmental program, metabolic balance and immune system of the human body, otherwise it may cause organ dysfunction or other pathological conditions. · In general, fundamentally changing the structure of the human respiratory system involves multiple frontier fields such as gene regulation, epigenetics, organ engineering, and stem cell biology, and requires long-term and in-depth exploration on laboratory animal models, which is still out of reach. [Summary] In general, although it is often described in science fiction works to give humans the underwater breathing ability of fish through gene editing, it is still in an extremely preliminary and even unrealistic stage in reality due to multiple technical, medical and ethical limitations. At present, gene editing technology is mainly used to treat genetic diseases, and safety, controllability and the impact on future generations are the research focuses. Any method that attempts to introduce non-human characteristics into the human body faces severe scientific problems and legal and ethical considerations. Therefore, for scientific researchers and society, we should maintain a cautious attitude, focus on safe, compliant and healthy medical applications, and strictly abide by relevant international and domestic laws and regulations.