Water resources have spurred the need for advanced maritime technologies, particularly for effective exploration and harnessing. Traditional maritime resource investigation methodologies are hampered by challenges such as elevated costs and risks. Unmanned Surface Vehicles (USVs) have emerged as a transformative solution, offering applications previously unattainable or challenging with conventional ships. An essential element in enhancing the capabilities of USVs is the incorporation of “Digital Twin” (DT) technology, a digital representation mirroring a system's real-world attributes and behaviours. While DT's application has gained traction in other sectors, notably in autonomous vehicles and unmanned aerial vehicles, a focused exploration of its integration in USVs remains sparse. This paper bridges this gap by offering a comprehensive survey of DT within the context of USVs. We review prevailing DT methodologies, delve into multifaceted perspectives surrounding DT-including definitions, classifications and key features, and highlight the prospective directions and challenges for its future application in USVs. Through this study, we underscore the potential of DT in enhancing the capabilities, productivity, and sustainability of USVs in complex maritime environments.