Two unfitted mesh methods for a linear incompressible fluid/thin-walled structure interaction problem are introduced and analyzed. The spatial discretization is based on different variants of Nitsche's method with cut elements. The degree of fluid-solid splitting (semi-implicit or explicit) is given by the order in which the space and time discretizations are performed.The a priori stability and error analysis shows that strong coupling is avoided without compromising stability and accuracy. Numerical experiments in a benchmark illustrate the accuracy of the different methods proposed.