The present study focuses on the modelling and design of a reconfigurable Autonomous Underwater Vehicle (AUV), intended for survey and hovering operations. The research activity is divided in two main areas of study: the control of the vehicle in survey configuration and the design of a mechanical assistance system for the reconfiguration process. The first part involves the development of a dynamic model for the system, with emphasis on kinematics expressed in quaternions, ensuring an efficient and singularity-free representation of rotations. Vehicle control is implemented through a PID controller for trajectory tracking, in order to evaluate the stability and precision of the system along predefined paths.