This study aims to analyze the effectiveness of environmental protection against seawater pollution in Indonesia and formulate the necessary legal and institutional reforms to optimize it. The main problems studied include how effective existing regulations are in tackling marine pollution and what reforms are needed to ensure that environmental protection can run optimally. This research uses normative legal research methods with a statute approach and a conceptual approach, which focuses on the analysis of Law Number 32 of 2009 concerning Environmental Protection and Management, Law Number 32 of 2014 concerning Marine Affairs, and various other related regulations. The analysis was carried out using the Theory of Legal Effectiveness to assess the extent to which the law is able to function effectively in society. The results of the study show that environmental protection against marine pollution in Indonesia has not been running optimally, caused by weaknesses in the legal substance, institutional structure, and legal culture. In terms of substance, there are still disharmony of regulations and weak sanctions arrangements. In terms of structure, there is an overlap of authority between institutions and limited law enforcement capacity. Meanwhile, in terms of legal culture, low awareness among the public and business actors has also worsened the condition of marine pollution. Therefore, the reforms needed include strengthening and harmonizing regulations, structuring and institutional integration, increasing the capacity of law enforcement officials, utilizing surveillance technology, and increasing community participation. Thus, the optimization of marine environmental protection can only be achieved through a comprehensive and integrated approach between legal and institutional aspects.