At the site of the Hong Kong-Zhuhai-Macao bridge project, the underwater stone bed needed compaction. However, conventional underwater dynamic compaction could not be used to tamp the scattering-filling rubble stone layer with no dead angle over a short period of time. Thus, vibrating compaction technology was used underwater for the first time in China. Owing to the scarcity of engineering examples, theoretical analysis was needed prior to field application. In this study, rubble stone layers and vibration systems were simplified to a mechanical model. The vibration equation was established, and through strict mathematical deduction, the vibration system's work on the rubble stone was obtained. The results show that the weakening effect of water on vibration compaction is very poor.