SpaceX is spending considerable effort to catch the Falcon 9 first stage onto a giant drone ship. I am aware that salt water ruins almost everything in the long run, but the first stage is a composite material and seems to be painted. If it can survive a 8 km/s reentry, it should be able to survive a little time in the water. Empty of all fuel, the Falcon 9 first stage way just 75,000 pounds. Considering how much surface area it has, it should be able to float. There are carbon fiber (and fiberglass) boats, so why can't the Falcon 9 stages just touch the water (even for brief time)?