Obtaining accurate information about the seawater temperature and visualizing it in real time is of great importance for aquaculture fishers, as water temperature fluctuations due to tide inflows greatly affect the development of fish and shellfish. Fishery researchers install a lot of multiple depth water temperature continuous observation equipment in the sea, and then, they collect and accumulate the data on the seawater temperature to realize its visualization. In this research, we develop a novel system to visualize the current conditions of seawater and its variations over time based on the collected water temperature data. Our system allows representing the most recent seawater temperature information and its variation over time in the forms of a table, graph and a three-dimensional temperature distribution chart through a web browser. In addition, in this system, it is possible to download the seawater temperature information measured during a period in the past. Our system can be used to improve the efficiency of feeding, thereby reducing the costs associated with aquaculture maintenance; moreover, it can serve to avoid damages caused by red tide and to prevent fish diseases.