Collaborative shipping is a horizontal collaboration mechanism where multiple independent shippers consolidate their freight flows to share the same set of transports to reduce cost. We propose collaborative shipping mechanisms without an orchestrator, using blockchain. The smart contracts identify the bundling opportunities, matches with the carrier using group decision making, and allocates the cost among the shippers using cooperative game theory mechanisms. The blockchain member nodes having stakes include representatives from shippers, carriers, and regulatory bodies. A proof-of-concept is implemented in Hyperledger Fabric for collaborative shipping of spot shipments.