  We consider a coupled PDE-ODE system describing the motion of the rigid body
in a container filled with the incompressible, viscous fluid. The fluid and the
rigid body are coupled via Navier slip boundary condition. We prove that the
local in time strong solution is unique in the larger class of weak solutions
on the interval of its existence. This is the first weak-strong uniqueness
result in the area of fluid-structure interaction with a moving boundary.
