Real-time hybrid substructuring (RTHS) is a relatively new method of vibration testing that allows a coupled dynamic system to be partitioned into separate physical and numerical components or substructures. The physical and numerical substructures are interfaced together in real-time as a closed-loop hybrid experiment similar to hardware-in-the-loop (HWIL) testing, whereby the physical substructure is tested concurrently with a numerical simulation of the remaining system. This work describes uniaxial RTHS testing at the University of Connecticut Structures Research Laboratory applied to simplified fluid-loaded structural systems. These tests use a physical one degree of freedom (DOF) mass-spring system coupled to a fluid-loaded analytical substructure. One test uses a fluid-loaded plate as the analytical substructure, while another test uses a fluid-loaded cylinder. An overview of RTHS is also presented, including the details of the feedback control architecture for coupling physical and analytical substructures together using servo-hydraulic actuation with a model-based minimum-phase inverse compensation (MPIC) of the actuator dynamics. In addition, a convolution integral (CI) method for solving the fluid-loaded analytical substructures in real-time is described. Experimental results demonstrate that RTHS can accurately capture the dynamic interaction of a fluid-loaded structural system and provide physical insight into the coupled response.