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We experimentally investigate the collective swimming behavior of Caenorhabditis elegans nematodes in viscoelastic media, focusing on bulk-averaged locomotion dynamics obtained from ensembles of approximately 100 individuals across multiple realizations. The study examines the hydrodynamic interactions among nematodes suspended in an agar-based viscoelastic fluid, considering different volume fractions of both the living organisms and the macromolecular constituents of the surrounding medium. The analysis includes the characterization of nematode size distributions, average beating frequencies, and the wavelengths of the traveling muscular waves that propagate along their slender cylindrical bodies. In addition, we determine the mean body curvature and the average propulsion velocity of populations of small nematodes, with body lengths ranging from approximately 100 to 500 μm, under low-Reynolds-number and high-Péclet-number conditions. The body-nematodes bending (muscular waves) effect on its self-propulsion is also observed and characterized. Scaling arguments based on balances of viscous, bending and elastic forces are also explored in this research. The rheology of the active suspension undergoing oscillatory shear of small and moderate amplitudes is largely explored regarding the viscous and elastic effects of the active particle collective motion. This video was produced at the Laboratory of Microhydrodynamics and Rheology of the Vortex Group, University of Brasília (Brazil). Related studies can be found in S. Malvar and F.R. Cunha, Physics of Fluids (2021), Rheologica Acta (2019), and Biomicrofluidics (2017), . The C. elegans nematodes used in this study were kindly provided by C. E. Winter (Department of Parasitology, University of São Paulo, Brazil). Y. G. Irilan & F. R. Cunha – Physics of Fluid, 2022.