Prediction markets are getting serious. That's why startup River Markets launched a platform that gives professional traders a single place to trade across multiple prediction markets. Co-founded by CEO Oscar Levy and CTO Antonin Parrot, River Markets announced Tuesday that it raised $8.5 million in a seed round led by Haun Ventures that closed in July. The announcement aligns with a broader industry trend as institutions increasingly view prediction markets as financial tools. According to River Markets' founders, meeting that demand at scale requires technology that lets firms trade across platforms and handle larger orders.