The decrease of nematode size with water depth is well documented in the literature. However, many nematode size datasets originate from bathymetric gradients, with strong bias towards deep-water, muddy sediments. This has narrowed our perception of the environmental factors that may influence nematode morphometry. Here we perform a morphometric analysis with data collected from a variety of sampling locations around Europe at a wider range of depths and sediment types. All nematode size descriptors decrease significantly with water depth, which explains more than 60% of total variation. This trend is most pronounced for mean nematode dry weight, which decreases with ~20% for every doubling in water depth. This coefficient of decrease is smaller than the described decline in food deposition with depth, as estimated from sediment community oxygen consumption rates (~35%), but in the same order as the decrease of nematode density. Order of magnitude estimates based on these trends suggest that nematodes contribute for about 7.5% to benthic metabolism over the depth range. In contrast to nematode dry weight, the decrease of nematode length and width with water depth is less steep. However, nematode length is also affected by grain size, where shallow-water coarse sediments are inhabited by longer nematodes. Nematodes from the oligotrophic Aegean Sea are characterised by low length values and high width values, probably as an adaptation to sediments poor in organic matter. These observations suggest that local factors can also be very important for shaping the morphometric landscape of the nematode communities.