Naturally occurring materials have long served as an inspiration for the development of new materials and technology. Consider the immune response to mechanical trauma to a blood vessel. The clotting cascade, particularly the formation of the platelet plug, is an intricate example of the assembly of macromolecules and microparticles involving interplay between mechanical stress and chemical reaction in a biological system. Synthetic (and biological) macromolecules are ideal building blocks for engineering complex hierachical nanostructured materials at solid-fluid and fluid-fluid interfaces. Electrostatic complexation and covalent crosslinking of these molecules can lead to the formation of supramolecular networks which confer unusal properties such as mechanical rigidity that is outside of the description of equilibrium surface thermodynamics. We study two dimensional fibrin networks synthesized on the air-water interface of pendant drops following the biochemistry in the final common pathway of the clotting cascade. These protein-based biomembranes typically have thicknesses less than 100 nm. Our measurements indicate strain-stiffening nonlinear elasticity and a nearly perfect elastic recovery for total strain up to 70% which is consistent with recent results for similiar networks reported by W. Lui et al. Science 313 (634) 2006. We also measure the impact of strain on the enzyme-mediated (streptokinase) degradation of the membrane and show a direct relationship between the rate of degradation and strain. We also describe experimental results for water transport through these nanobiomembranes as a function of strain.