Due to the unavoidable movement of nodes within oceanic environments and the continual changing of underwater sound speed, it is difficult to synchronize clocks between nodes and locate them. Therefore, this paper proposes a joint time synchronization and localization mechanism (JTSL). Firstly, a time synchronization method is proposed based on three autonomous underwater vehicles (AUVs). In this method, AUVs send synchronization request signals to the moving unknown node three times. The clock skew and offset of each AUV compared to the clock of the unknown node are obtained based on the information transfer delay between nodes as sound speed changes. After time synchronization, the unknown node receives location information from AUVs and obtains the sound speed change function. Based on this function and kinematic equations, a distance calculation method is developed to calculate the distance between the unknown node and AUVs. In addition, a multi-layer fast meshing localization method is designed to improve the accuracy and speed of node localization. The simulation experiments show that JTSL can overcome difficulties related to time synchronization and localization of mobile nodes, and it demonstrates excellent performance in terms of time synchronization accuracy, energy efficiency, localization accuracy, and localization time.