  In this paper we analyze the interaction of an incompressible Newtonian fluid
with a linearly elastic Koiter shell whose motion is restricted to transverse
displacements. The middle surface of the shell constitutes the mathematical
boundary of the threedimensional fluid domain. We show that weak solutions
exist as long as the magnitude of the displacement stays below some (possibly
large) bound which is determined by the geometry of the undeformed shell.
