At the microscale, hydrodynamic constraints lead to nonintuitive features of propulsion for living systems. First, I'll discuss how characteristics of low Reynolds number microscale flow constrain the approach of swimming microorganisms to suspended target particles, which can be important for life processes including feeding, mating, and finding new habitats. Second, I'll examine a case in which the bacterium Helicobacter pylori actively creates a heterogeneous complex medium as it swims through gastric mucus by generating ammonia that locally neutralizes the acidic gastric environment, turning nearby gel into a fluid pocket. We estimate the size of the fluid pocket. Last, I'll discuss in-progress experiments on burrowing through granular media, in which we develop systems to photoelastically visualize how organisms from the centimeter scale to 100 micron scale generate and interact with force chains as they burrow.