The purpose of this report is to assess methodologies for evaluating plastic waste flows and leakage into the environment, specifically focusing on plastic leakage into waterways and oceans. We conducted a literature review on current plastic waste evaluation methodologies and investigated 18 methodologies out of a range of models and tools. We used specific criteria to select the best platforms and available models. Our study focused on methodologies that assess at a geographical level rather than those focusing on the corporate level. We also considered the operability of the method, looking for those that are usable at various levels, not just in scientific research. Additionally, we evaluated the validity of the model based on its publication in high ranking scientific journals or by well-known international institutes/organizations. We also took into account the completeness of the model, ensuring it covers a range of plastic sources and their leakage pathways.