Heavy Water: Filming of Kevin Costner’s next project, Waterworld, is two months away, and already it’s proving to be one of the most challenging movies ever made. Or, at the very least, the wettest. The main set for the $60 million futuristic adventure-basically a floating Road Warrior, with Costner hunting for land in an ocean-covered world-is a huge, doughnut-shaped floating city weighing close to a million pounds that is currently under construction on Hawaii’s Kona coast. Meanwhile, director Kevin Reynolds (Robin Hood: Prince of Thieves), who suffers from seasickness, is looking at roughly 120 days of filming-on water. ”We’re trying to find some doctor (for) a magical cure,” says Reynolds.