Plastic pollution in aquatic ecosystems causes enormous concern due to its rapid dispersion and persistence in the environment. The marine Antarctic system does not escape this worldwide problem, as macro and microplastics in surface waters and marine-coastal zones have already been detected, which can result in a significant threat to this environment and its fragile fauna. However, the magnitude and sources of this threat in the Antarctic are far from being understood, and for this, the generation of basal information has been identified as a priority. This study aims at evaluating the presence of microplastics in surface marine water samples of Maxwell Bay (King George island, 62º 11´4´´S and 58º 51´7´´O), between 2016 and 2019. Water samples were taken with a Manta net (220 microns) in three different areas, one in front of the Collins glacier, another in front of the Uruguayan Antarctic Base, and a third at the adjacent bay Caleta Norma. Shape, colour, size and density of microplastics were analysed with polarized light microscopy, in the three replicates taken in each area. Microplastic densities varied between 4.4-30.5 items.m-3, which represents a difference of at least one order of magnitude higher with other Antarctic studies. We found no differences between sampling areas or years. Fibers were the most represented shape in each year and area sampled. In general, the average percentage of fibers and fragments in each area and year had a relation of approximately 90% of fibers and 10% of fragments, except for one site (1-2017) that had 68.2% and 30.7%, respectively. The sizes of the fibres oscillated between 0.001-4.92 mm and the fragments between 0.039-3.12 mm. Our results provide basal information that contributes directly to the objectives and challenges of the Antarctic Treaty System.