This book places the Bay of Bengal at the center of Asian and global history. Sunil S. Amrith argues that the Bay of Bengal has long been a region connected by migration, trade, culture, and environmental forces. The book integrates human history with environmental history to explain how monsoons, storms, rivers, and the sea shaped the lives of millions of people.

A major focus is the large-scale migration of people across the Bay between the nineteenth and twentieth centuries. Millions of Indians, particularly from South India, moved to places such as Burma (Myanmar), Malaya, Singapore, and Sri Lanka in search of work and opportunity. The book examines their experiences, the growth of multicultural port cities, plantation labor systems, and the social and economic networks that connected South and Southeast Asia.

The author also explores the impact of colonialism, global capitalism, and technological changes such as steamships on regional mobility. By the 1930s, economic crises, nationalism, and changing political boundaries weakened many of the older patterns of movement and exchange.

In its final sections, the book addresses contemporary concerns such as climate change, rising sea levels, environmental vulnerability, and the future of the Bay of Bengal region. It argues that understanding the region's interconnected past is essential for addressing Asia's future challenges.