Ships are prone to icing when navigating in polar low-temperature environments. Excessive ice accumulation can affect ship stability, operational safety, and operability of deck equipment, posing a serious threat to crew safety and hindering the rational development and utilization of polar regions. Ship icing is mainly caused by the splashing of waves, and its physical process can be regarded as the freezing process of a large number of saltwater droplets on a cold surface. Experimental research on the freezing process of a single saltwater droplet is essential for deeper understanding of the mechanism of ship superstructure icing at the mesoscale. For this, experiments are conducted on the freezing and melting of freshwater droplets on cold surfaces, the progress of the phase interface during the freezing process of freshwater droplets, the shape changes of water droplets after freezing, the freezing and melting time are recorded, and the influencing factors of the freezing process of freshwater droplets are analyzed. A saltwater droplet freezing experiment with a 3.5% mass fraction is also conducted, the shape changes, freezing and melting times after freezing are recorded, and the impact of droplet volume and cold surface temperature on the freezing process of the saltwater droplets are analyzed and discussed. The influence of salinity is analyzed and compared by comparing the freezing and melting experimental results of saltwater with those of freshwater droplets. The research outcome can provide data support for the validation of ship icing prediction models and scientific guidance for the development of anti-icing and deicing technologies on structural surfaces.