Biological organisms have evolved unique reversible adhesion mechanisms to grip onto challenging substrates. Frogs and toads use a soft, porous tongue infused with viscoelastic saliva to capture slimy, dusty, or feathery prey. Octopuses, clingfish, and remora fish combine suction cups with micro-papillae or thick mucus to reduce leakage across the seal and grip onto slippery and scaly substrates. Reversible adhesion in biology is often a collaboration between soft tissues and fluid adhesives, leading to grip solutions that can easily adapt to unpredictable environments. We seek to characterize these robust biological adhesive mechanisms using morphological characterization, modeling and simulation, and experimental validation. Thick bio-fluids like frog saliva are characterized using a combination of shear and elongation rheology. We explore the potential of measuring bio-fluids on-site with a custom, portable rheometer that reduces the critical time between sample collection and testing. The role of tissue softness in adhesion is measured using micro-indentation pull-off techniques. For reversible underwater adhesion, we develop a modular apparatus that can test the longevity and strength of underwater grippers with variations in substrate and environmental conditions. Using a system of cameras, and force, pressure, and flow rate sensors, we identify and characterize failure criteria for grippers that utilize suction adhesion. By understanding how these reversible adhesive mechanisms grip onto challenging substrates, we look to address today’s challenging grip problems through development of versatile and resilient artificial grippers.