The existing engineering properties of soils cannot always provide sufficient strength and optimization, resulting in the need for soil improvement. There are many methods and additive materials currently used in soil improvement. However, if the method to be used includes an alternative additive material, the material's sustainability, environmental friendliness and low cost play a major role considering the increasing world population and energy need. At the same time, the increasing population's demand for energy and the resulting increase in the number of energy structures increase the interaction of the soils with temperature. When all these are evaluated together, seaweed-added mixtures, terminologically known as "Zostera marina", were created within the scope of this study and their hydraulic conductivity behavior was examined under room and high temperatures. Dried seaweed is a sustainable, low-cost marine plant that has been used for thermal insulation for years in countries with a cold climate, such as Denmark. In this study, seaweed additive was added to zeolite-bentonite mixtures and hydraulic conductivity tests of the mixtures were determined under room and high temperatures (40°C). Thus, the effects of additive and temperature effects on permeability were examined separately. The test results showed that the seaweed additive had a reducing effect on hydraulic conductivity behavior at room temperature, while permeability increased under high temperature, parallel to the literature.