""Alien Oceans"" explores the intriguing possibility of life thriving in the subsurface oceans of icy moons like Europa and Enceladus, challenging our Earth-centric view of habitability. It delves into what makes an ocean habitable, even without sunlight, and how we might detect life on these distant worlds. The book highlights that the convergence of water, energy, and essential chemical elements on these moons may create plausible habitats, potentially detectable through novel biosignatures. This captivating exploration starts by introducing fundamental concepts of habitability, such as the role of water and alternative energy sources. It then scrutinizes Europa and Enceladus, examining evidence for their subsurface oceans and potential energy sources like hydrothermal vents, based on data from missions like Galileo and Cassini. The book uniquely focuses on the challenges of detecting life in these extreme environments, considering novel approaches to sampling and data interpretation. Finally, ""Alien Oceans"" progresses by discussing strategies for future exploration and life detection, including robotic missions and remote sensing techniques. The book ties together astrobiology, oceanography, and planetary science, providing a comprehensive and accessible overview of the search for extraterrestrial life in our solar system, making it valuable for anyone interested in space exploration and astrobiology.