In order to assess water quality, it is necessary to define the basic hydrogeochemical properties and governing elements of groundwater chemistry, which are crucial to knowing the whole groundwater ecosystem. Extensive agricultural activitiessignificantly impact groundwater chemistry, influencing chemical composition and spatial distribution, revealing mechanismsof contamination and transformation through agricultural environments. This chapter explores the hydrogeochemicalcharacteristics of the groundwater of the three catchments (i.e., Maputaland or upper, uMhlathuze or middle, and Tugela orlower) situated in the eastern coastal region of South Africa. The hydrogeochemical properties of groundwater in three separatecatchments demonstrated differences in water type influenced by natural processes and human activities. According to majorion chemistry, Piper, and Chadha plot interpretation, most of the water facies were determined as Cl-Na facies, suggestinggradual saltwater contamination and ion exchange. Different levels of seawater intrusion are confirmed by theSeawater Mixing Index (SMI). The coastal catchment exhibits the greatest SMI values, which align with higher concentrationsof Cl– and Na+. Statistical investigation utilizing SPSS, encompassing principal component analysis (PCA), determined primarypollutant sources, differentiating between runoff from agriculture (elevated NO3–, K+), industrial effluents,and seawater intrusion.