The purpose of this study is to find the suitability of seaweed cultivation land on Lembeh Island and its surroundings. The data collection technique in this study was divided into several events, namely primary data collection, where the implementation was carried out in the field such as conducting a ground check from the results of the analysis. In addition, there are also secondary data that generally come from local government data related to this study. In this study, the type of data used was data related to seaweed cultivation such as: protection, basic substrate, temperature, pH, current, depth, MPT, DO, salinity, phosphates, and nitrates. Based on these data, interpolation will be carried out which aims to predict grid values that are not represented by sample points. The interpolation used is Inverse Distance Weighting (IDW). The percentage of suitability of seaweed cultivation in the waters of Lembeh Island and Bitung City has 2 categories. The Unsuitable (N) has a percentage of 41%, and for the Category Suitable (S1), which is a highly recommended zone for seaweed cultivation, has a percentage of 59%. The percentage of this very suitable area is an area that is still classified as safe from sea transportation activities in Bitung City.