Abstract: An underwater explosion bubble contains enormous energy, which can cause severe localized damage to structures in near-field scenarios. To fully utilize the damage potential of such bubbles, this paper proposes a synergistic impact method based on spatiotemporal control of two out-of-phase underwater explosions. The total charge is divided into two independent explosive sources. By precisely adjusting their relative spatial configuration and initiation delay time, the interaction between the shock waves and bubble oscillations is used to achieve an enhanced and synergistic impact on the target structure. A series of experiments are conducted to compare a reference single-charge underwater explosion with three specially designed two-charge configurations. The results demonstrate that the proposed two-charge scheme with an unequal charge distribution significantly amplifies the jetting and collapse loads exerted by the primary bubble on the structure. Under the same total charge mass, this out-of-phase two-bubble configuration achieves a markedly superior impact effect compared to the traditional single-charge explosion. These findings provide theoretical insights and experimental references for the development of novel bubble control techniques in underwater explosions.