Underwater mobile sensor networks (UMSNs) with free-floating sensors are more suitable for understanding the immense underwater environment.Target tracking,whose performance depends on sensor localization accuracy,is one of the broad applications of UMSNs.However,in UMSNs,sensors move with environmental forces,so their positions change continuously,which poses a challenge on the accuracy of sensor localization and target tracking.We propose a high-accuracy localization with mobility prediction (HLMP) algorithm to acquire relatively accurate sensor location estimates.The HLMP algorithm exploits sensor mobility characteristics and the multistep Levinson-Durbin algorithm to predict future positions.Furthermore,we present a simultaneous localization and target tracking (SLAT) algorithm to update sensor locations based on measurements during the process of target tracking.Simulation results demonstrate that the HLMP algorithm can improve localization accuracy significantly with low energy consumption and that the SLAT algorithm can further decrease the sensor localization error.In addition,results prove that a better localization accuracy will synchronously improve the target tracking performance.