Environmental parameters affecting plant productivity and microbial respiration, such as water level, salinity, and groundwater temperature included in these datasets, are key components of wetland carbon cycling, carbon storage, and capacity to maintain elevation. Data were collected to (1) provide background data to evaluate potential differences in water level and carbon flux between wetland sites with differing elevation and tidal inundation and (2) facilitate applications of Blue Carbon projects in coastal wetlands. Associated child pages include continuous water level, salinity, and temperature from shallow wells installed in coastal wetland sites on Cape Cod, Massachusetts. These datasets are grouped by the project they support or by study site. Project study sites include salt marshes with natural tidal flow, salt marshes that were previously tidally restricted and have been restored, impounded coastal wetlands with restricted tidal flow inclusive of various vegetation types, and Phragmites dominated areas fringing natural salt marshes.