This paper deals with L 1 adaptive control of a novel omnidirectional underwater vehicle called MEROS. To the best of our knowledge, this is the first study of depth and attitude (i.e. φ, θ, and ψ) tracking control on an underwater vehicle. We experimentally prove the effectiveness of the proposed control approach by commanding in closed-loop simultaneously the four aforementioned degrees of freedom (DoFs). The dynamic model of MEROS is highly nonlinear with coupling effects between the different DoFs making its stabilization and tracking control more challenging than conventional ROVs (remotely operated vehicles). Therefore, the use of a robust controller becomes essential, and the proposed scheme allows to ensure robustness whilst fast adaptation is achieved. Real-time experiments are performed to show the effectiveness of the proposed control design.