Described herein are compositions useful for controlling fluid flow, for example in a target zone of a subterranean environment, and methods of forming and using the same. The composition generally comprises a quantity of fibers and a quantity of swellable particles, which may be dispersed in a carrier fluid. The composition may be synthesized in the form of a bulk gel or may be gelatinated during use. The fibers in the compositions provide improved performance as compared to prior PPG and RPPG particle-containing compositions. Specifically, the compositions reinforce the re-cross-linked/re-associated hydrogel plug in underground features and support proper rehydration of RPPG particles with water or brine to better to provide structural support for the particles within the gel and to more completely fill underground void space conduits.