Wrongful death cases filed over the fatal sinking of a duck boat in July were paused after Ripley Entertainment Inc. invoked a 167-year-old federal law designed to encourage investment in steamships.

Orlando, Fla.-based Ripley and its affiliate Branson Duck Vehicles LLC filed the notice of stay in the U.S. District Court for the Western District of Missouri Dec. 5, attaching an order by another judge of that court considering the separate maritime action.

The move isn’t likely to succeed in...