The volume examines how seas and oceans connect geographically as also through networks of trade, cooperation, beliefs, scientific knowledge and rumour. It emphasises open spaces rather than land boundaries and thus decolonises regional history and accentuates the difference between marine and maritime worlds. Focusing on the Pacific, Atlantic and the Indian Oceans and the Mediterranean Sea in Europe, it calls for a re-conceptualisation of maritime history. Viewing waterscapes as autonomous bodies, it studies mobility and paths of cultural transmission—how people and goods are conveyed across waters, the imagined unities of people in terms of locals and diasporic populations, and the establishment of regions, trading blocs and empires. It takes up diverse themes like role of the Portuguese in the making of world history and Portuguese overseas expansion, the Indian Ocean in the European trading horizon and Thai trade in the Indian Ocean.