The present case study discusses the subgrade enhancement strategies for highly saline marine soils located at Bhavnagar District, Gujarat, India. In addition to the presence of various salts, the saturation levels of these soils were observed to vary throughout the year due to several climatic and geographical factors. Initially, the unsaturated behaviour is evaluated using the standard filter paper method. Due to the low in situ California bearing ratio (CBR) value (1.62%), locally available fly ash (10%-30% by weight) was used to improve the strength and stiffness of the soil. Addition of fly ash resulted in the considerable reduction of salinity and suction levels at all dosages of fly ash. The unconfined compressive strength (UCS) and CBR have increased until 20% fly ash and reduced from thereof. The maximum CBR obtained was about 9%, which can withstand low to medium volumes of traffic. However, the UCS developed at seven days was observed to reduce at 28 days. This may be due to the secondary reactions and change of form of salts present in the matrix. Henceforth, further investigations on interactions at micro-level, formation of secondary compounds, and suction levels were recommended to prepare a sustainable subgrade in this terrain.