This paper studies how the interactions between ships and exporters in the global shipping markets influence commodity flows and prices. We develop a multi-market search and matching model in which ships and exporters optimise their behaviours in response to market-specific and idiosyncratic shocks: unloaded ships can search for jobs in their market of last contract or ballast to some other market. Market-specific trade shocks induce net movements of ships out of markets hit by unfavourable shocks, while idiosyncratic taste shocks ensure gross flows between markets through ballasting are always positive, a prediction consistent with the data. Using detailed AIS data, we construct a unique shipping dataset which tracks tankers’ movements, loading status, and employment history. Leveraging it, we structurally estimate our model to study the market-switching behaviours of ships in the context of recent global trade disruption, and to recover a time-path of trade shocks and corresponding commodity flows and prices.