What is the fine-grained topic of the following text: Within hours of the news, not only had MarineMax lost 11% of its market cap, but also boat builder Marine Products (NYSE:MPX) had lost 5% of its own value out the porthole -- and that has only accelerated, with the firm now trading a good 12% lower than it did at Friday's close. Only return the topic.
Stock market performance of MarineMax and Marine Products