This article examines how the Chinese political and academic discourses have constructed a narrative of China as a peaceful maritime power and the role that underwater archaeology has played in narrating China's rise. The ancient Chinese concept of tianxia (天下) is a central part of the Chinese elites’ discourse on maritime policy. This concept, translated as “all under heaven,” forms part of China's effort to produce historical statecraft using textual sources and underwater archaeological artefacts. In this narrative, the historical figure of Zheng He became a prominent representative of China's peacefulness, refuting concerns regarding the purposes of a more assertive Chinese foreign policy. Studying tianxia under the sea thus contributes to forming a better understanding of the production of narratives respecting China's rise. In particular, underwater archaeology is highlighted as an authoritative source of evidence underpinning and reinforcing narratives of China as an ancient and peaceful maritime nation.