A fluid sampling and measuring assembly has: a sampling and measuring module configured to sample and analyse a fluid sample; a picking module configured to contain the fluid sample; at least one navigation module configured to navigate in the body of water; and at least one interface module configured to hydraulically connect a sampling station, the sampling and measuring module and the picking module. The sampling and measuring module and the picking module are configured to be mechanically and hydraulically coupled to each other and to the sampling station to take and analyse the fluid sample and the picking module is configured to be coupled to the navigation module to transfer the fluid sample to an analysis laboratory.