The maritime economy is becoming increasingly important. Added to this are the challenges posed by climate change. It is of enormous importance to continuously research new technologies and processes for the maritime sector in order to make a contribution to the environment and humanity. The laser is an established tool in many branches of the industry and can also be used under water. The paper gives an overview of 4 applications of lasers in the maritime sector. These include underwater cutting, defusing explosive ordnance in the sea, cleaning fouling from ships and analyzing materials in the deep sea. The focus lies on the challenges of laser processes underwater but moreover shows the possibilities to save our environment, reduce energy costs and rise safety for people and animals.