This manuscript addresses trajectory tracking problem of autonomous underwater vehicles (AUVs) on the horizontal plane. Adaptive sliding mode control is employed in order to achieve a robust behavior against some uncertainty and ocean current disturbances, assuming that disturbance and its derivative are bounded by unknown boundary levels. The proposed approach is based on a dual layer adaptive law, which is independent upon the knowledge of disturbance boundary limit and its derivative. The approach tends to play a significant role to reduce the chattering effect which is prevalent in conventional sliding mode controllers. To guarantee the stability of the proposed control technique, the Lyapunov theory is used. Simulation results illustrate the validity of the proposed control scheme compared to the finite-time tracking control method.