This paper investigates the influence of ocean currents on the motion characteristics of underwater unmanned vehicles (UUV) operating in complex current environments within shallow waters. First, based on the characteristics of shallow-water currents, mathematical models are established for both laminar and turbulent flows. Subsequently, a UUV motion model incorporating current effects is developed. Utilizing this model, simulation analyses of spiral diving motion characteristics are conducted under both laminar and turbulent flow conditions to explore the impact of shallow-water currents on UUV motion. Simulation results demonstrate that shallow-water currents directly affect the UUV motion characteristics, altering its velocity and attitude angles, consequently leading to trajectory deviation and changes in turning radius. Under laminar flow, the trajectory deviation direction aligns primarily with the current direction angle but differs from the wind direction angle. The combined action of steady and gusty winds increases both the deviation distance and turning radius. Under turbulent flow, trajectories exhibit random deviations and oscillations. Here, the turbulent mean velocity dominates the deviation magnitude, while the turbulent intensity influences both the fluctuation range of the deviation and the variation amplitude of the turning radius. As turbulent intensity increases, the horizontal and vertical trajectory deviations increase to 11.105 m and 2.004 m, respectively, and the turning radius increases from 4.578 m to 8.097 m. These findings provide a theoretical basis for path planning and adaptive control strategies of UUV in shallow-water regions, demonstrating practical engineering value.