With the opening of the Arctic shipping routes and the growing number of Arctic scientific research expeditions, the demand for novel auxiliary icebreaking methods is also increasing. High-pressure water jet, as an efficient and clean auxiliary icebreaking modality, has received widespread attention. At present, some research has been conducted on non-submerged jet icebreaking for surface ships. However, research on submerged jet icebreaking for underwater vehicles has not yet been carried out. Therefore, this paper conducted a series of submerged highpressure water jet icebreaking experiments to discuss the influence laws of the submerged environment on the load characteristics and ice-breaking mechanisms and modes of the water jet. On the basis, the mechanism of ice breaking by submerged cavitating jet load, including flow field load, water hammer pressure and cavitation pressure, was analyzed, as well as the jet-ice interaction modes under multi-load contributions and the influence of related parameters. Finally, this paper experimentally verified the ice-breaking capability and efficiency of submerged water jet. Due to the shear cavitation between the submerged jet and the surrounding fluid, it had superior performance in continuous ice breaking compared to non-submerged jets and could be used as one of an auxiliary ice breaking methods for underwater vehicles.