This PhD project assessed the potential environmental impact of innovative GasDrive ships with more efficient and cleaner engines that release exhaust gas underwater to reduce water resistance by air lubrication. CO2 in the exhausted gas was identified as the major impactor and caused acidification. This had a significant community impact via direct effects on invertebrate species and indirect influence on the less sensitive species via the food chain. Especially less sensitive microalgae will profit from CO2 as micronutrient, potentially inducing an algal bloom especially with reduced grazer presence. Based on these findings a preliminary risk assessment of underwater released exhaust CO2 was carried out from a global marine perspective. In the worst-case scenario, adverse environmental effects are to be expected in the busiest shipping lanes only. Further attention should be given to the occupational risk for the crew, the potential antifouling effect and the generation of underwater noise.