This paper briefly reviews the environmental and hydrogeological factors influencing the tidal mangrove marshes. The characteristics of sedimentation structure, hydrodynamics and groundwater hydrogeochemistry in Dongzhaigang Mangrove Marsh are presented for two transects: one is a mangrove marsh, the other is a bald beach. Field measurements show that pH and ORP in the mangrove transect are generally higher than those in the bald beach transect, while the former’s TDS is lower than the latter’s, and that the variation scope of shallow water quality is greater than that of deep water quality in the mangrove transect, while it is very little in the bald beach transect. Further analyses indicate that both transects are subject to the same tidal action and have the same tidal environment. The difference between the two transects is the inland freshwater recharge conditions. Along the mangrove transect, there is significant freshwater from inland. We conclude that the bald beach not to be covered by mangrove plants is due to the lack of freshwater and saltwater recharge envionrment to be suitable to mangrove growth.