This article focuses on the underwater cultural heritage (UCH) located across the Pacific Ocean by sampling three temporal themes: living heritage and traditional indigenous cultural heritage, the global connections of the Manila Galleon trade, and the modern warfare of World War II (WWII). Many of the traditional cultural practices (living heritage) and tangible cultural heritage related to indigenous people of the Pacific are coastal and sea related. Their world encompasses the sea, which was not seen as a barrier as but a much-used connection to people occupying the thousands of islands. The Pacific contains an extensive maritime cultural heritage, including UCH, which reflects the cultural identity of people living in the region. From the 16th to 18th centuries, the Spanish Empire prospered through an elaborate Asia-Pacific trade network. The Manila Galleon trade between Manila, Philippines, and Acapulco, Mexico, connected into the existing Atlantic trade transporting commodities such as porcelain, silver, spices and textiles from Asia to the Americas and Spain. Of the 400 known voyages between 1565 and 1815, approximately 59 shipwrecks occurred, of which only a handful of galleons have been investigated. The scale of WWII heritage in the Pacific region reflects the intensity and impacts of global conflicts fought across the world’s largest ocean. Associated UCH includes near shore defensive infrastructure, landing and amphibious assault craft, submerged aircraft, and a wide range of ships and submarines, auxiliary, combatant and non-military casualties alike. Twentieth century warfare involved massive losses of material. The legacy of submerged battlefields in the Pacific is complex. Interest is high in the discovery of naval UCH, but critical aspects are often intertwined. Archaeology, history, reuse, memorialisation (gravesites), tourism, unexploded ordnance, environmental threat (fuel oil), ownership and salvage all shape what we can learn from this resource.