This paper presents the main results of the European H2020 WiMUST project, whose aim was the development of a system of cooperative autonomous underwater vehicles and autonomous surface vehicles for geotechnical surveying. In particular, insights on the overall robotic technologies and methodologies employed, ranging from the communications and navigation framework to the cooperative and coordinated control solutions are given. The software architecture and the lessons learnt from the preliminary field test are also discussed. Finally, field results of the final survey campaign carried out in the Atlantic Ocean are presented, demonstrating how a team of seven robots could autonomously conduct a geotechnical survey, producing seismic images without artifacts.