With the increase in the world population, there is an increase in the number of buildings and residential areas opened for use. However, in terms of engineering properties, there are many weak soil groups on the earth and it is not possible to use these soils without improving them. For example, it is known that clayey group soils have a high settlement problem and have low bearing capacity. These soil properties can be improved by using different additives in these soils. Where sustainability is also very important, the use of additives to be used in soil improvement as waste material or the selection of plant origin will provide an environment-friendly work that increases efficiency. In this study, it is aimed to optimize the zeolite-bentonite mixtures by determining the compression behavior at room temperature and 40°C using seaweed additive, that is, Zostera marina additive with its terminological name. Considering the areas where the soils will be used, it is aimed to examine the behavior of the average temperature value (~40°C), such as solid waste storage areas, around energy structures. Zostera marina has never been used for soil improvement before. However, it is a sea plant that has been used for many years in construction-related areas such as thermal insulation on the roofs of buildings in countries such as Denmark. Its resistance to thermal changes, its ability to preserve its organic structure without deterioration and for a long time, and its resistance to tensile and rupture show that soils can positively affect many engineering parameters such as compressibility and shear strength. The test results have shown that Zostera marina positively affected the compression behavior of zeolite-bentonite mixtures.