Fish sperm energetics were explored in this study to understand how sperm cells use energy to swim towards eggs for fertilization. The research found that fish sperm rapidly exhaust their energy while swimming, which is controlled by chemicals in their environment and their internal ions. The study also revealed that fish sperm use their electro-chemical potential to manage their energy levels and that they swim very efficiently for a short period in freshwater but for a longer duration in marine environments. Additionally, the study highlighted the importance of the physical energy required for fish sperm flagella movement and how sperm navigate towards eggs through chemotaxis. Overall, this research sheds light on the energy dynamics of fish sperm and how they power their movement in different aquatic environments.