The expansion of the trading scale of aquatic products has led to the widespread application of blockchain technology in product traceability and data sharing. However, the inability of data exchange and sharing between blockchains constructed in different enterprises or different links within the same supply chain has led to the persistence of information silos. Therefore, a cros-chain transaction model for aquatic products was proposed based on a notary mechanism, aiming to achieve cross-chain transactions between different links of aquatic products, solve single point of failure problems, and enhance transaction efficiency. Meanwhile, addressing the characteristics of cross-chain transactions for aquatic products, a two-stage cross-chain transaction process was proposed, along with an improved transaction error handling mechanism, to address the requirements of data consistency and atomicity during cross-chain transactions. A system prototype was built based on the Hyperledger Fabric platform. Experimental results demonstrated that under high transaction volumes, the average success rate of transactions exceeded 99%, with an average latency of around 0.21 s. Thus, the model met the requirements of cross-chain transactions.