This book represents six years of working experience as a marine professional within the marine offshore environment of the Gulf of Guinea. Having a keen interest in the growing environmental changes, my research interest was supported by conducting a PhD research study, examining the nature of the marine environment, the nature of offshore habitats and populations estimates, and the current anthropogenic events associated thereof. Therefore, this study describes the nature of the marine environment offshore within the Gulf of Guinea, the growing interest in non-renewable resources particularly hydrocarbons leading to the deepwater field developments by adjacent coastal nations.The study further identifies and describes the living marine mammals found in the offshore operations within a given period. this it does by attempting ecological population estimations.The study concludes by examining the type of marine operations that take place, how such operations impact the environment and lives. A recommendation is then arrived at on various anthropogenic stressors concerning the marine ecology and contribution to Global Warming Potential.