# Shadow Fleets: A Growing Challenge in Global
## 1 Introduction  
Shadow fleets, operating beneath the veil of international regulation, have long been a clandestine feature of global maritime commerce. While not a new phenomenon, these fleets have gained unprecedented prominence and scale in recent years, particularly in the wake of recent geopolitical events and international sanctions. The International Maritime Organization [1] defines a 'dark fleet' or'shadow fleet' as ships engaged in illegal operations aimed at circumventing sanctions, evading compliance with safety or environmental regulations, avoiding insurance costs, or engaging in other illegal activities. A key characteristic is their deliberate effort to avoid detection, often by switching off their Automatic Identification System (AIS) or Long-Range Identification and Tracking (LRIT) transmissions, or by concealing the ship's actual identity. This comprehensive definition underscores the multifaceted nature of shadow fleet operations and the various ways in which these vessels operate outside internationalnorms and regulations established under the United Nations Convention on the Law of the Sea (UNCLOS) and associated ocean governance frameworks. From the perspective of international relations theory, particularly regime theory and compliance mechanisms, shadow fleets represent a fundamental challenge to established ocean governance structures where regulatory gaps and enforcement limitations create opportunities for non-compliance with international maritime law. The use of subterfuge tankers is not new in the oil trade, with similar tactics observed in Iranian and Venezuelan oil exports, providing historical precedents for current operations [2; 3]. This research addresses a gap in the field through the analysis of multiple empirical cases from 2022 to 2024, a period marked by the unprecedented expansion of shadow fleet activities following the Russian invasion of Ukraine. Our investigation examines established sanctions evasion tactics while documenting new operational patterns that emerged in response to international sanctions. As mainstream shipping companies and insurers withdrew from the Russian oil trade to comply with Western restrictions, a new ecosystem of opaque operators emerged to facilitate Russian sanctions evasion on an unprecedented scale [4; 5; 6]. Despite the growing significance of shadow fleets in global maritime trade, a critical research gap persists in the precise definition and categorization of this evolving phenomenon. Recent geopolitical events have not only expanded the scale of shadow fleet operations but have also diversified their nature and tactics, outpacing existing conceptual frameworks. To address this gap, our research proposes an innovative conceptual framework that introduces a more nuanced definition of shadow fleets. We posit that the term'shadow fleet' encompasses a spectrum of covert maritime activities, which can be primarily distinguished between 'dark fleets' and 'gray fleets'. This distinction is crucial in understanding the varying degrees of illicit activities and the complex strategies employed by these vessels. 'Dark fleets' and 'gray fleets' represent two distinct categories of covert maritime operations that operate outside or within the fringes of international regulations. 'Dark fleets' are vessels that engage in wholly illicit activities, deliberately avoiding detection and compliance by disabling their AIS transmitters, falsifying documentation, and frequently changing flags to evade regulatory oversight. These ships operate completely outside legal frameworks, often involved in activities such as sanctions evasion, illegal trade, and unregulated fishing. In contrast, 'gray fleets' exploit legal ambiguities and regulatory loopholes to operate in a zone of questionable legality. While these vessels generally maintain active AIS transmitters and adhere to a semblance of compliance, they manipulate data and engage in practices that skirt the edges of international law.