This commentary explores how blockchain technology is being leveraged to improve marine conservation and fisheries supply chain management globally. In doing so, the paper considers the technical and political challenges of building trust and equity for various stakeholders. A blockchain is a smart electronic database, distributed to all users, immutably tracking every transaction that has ever taken place on the network. The blockchain is very difficult to hack, with no single point of authority to make mistakes and collapse the system. Automated consensus protocols enable data transmitted on the network to be verified and stored immutably, minimising the risk of data corruption to near-zero. Blockchain is being increasingly hyped for a range of services and industries, including transparent resourcing for marine conservation, reducing pollution from plastics, reducing slavery at sea, and sustainable fisheries management. Public distrust in some conservation operations, as well as in the provenance of seafood, is growing. Although some global marine conservation organisations and seafood producers have found practical solutions in disruptive technologies like blockchain, riding this wave will only prove worthwhile if coastal communities and artisanal fishers are on board and stand a chance of landing a fair share of the benefits.