Members of this group are colourless with a head and up to thirty-two similar body segments composing an elongate trunk. The swimming appendages are lateral on each segment, and the animals swim on their backs. They are generally slow-moving. They have fangs connected to secretory glands; it is still unknown whether these glands secrete digestive juices or poisonous venom, or whether remipedes feed primarily on detritus or on living organisms. They have a generally primitive body plan in crustacean terms, and have been thought to be a basal, ancestral crustacean group. However, Fanenbruck et al. (2004) showed that at least one species, Godzilliognomus frondosus, has a highly organised and well-differentiated brain, with a particularly large olfactory area (not surprising in a species that lives essentially without light). The size and complexity of the brain suggested to Fanenbruck et al. that Remipedia might be the sister taxon to Malacostraca, regarded as the most advanced of the crustaceans. This is also one of the reasons why it is included in the Pancrustacea hypothesis, a hypothethical clade of probably the most advanced Mandibulata.
They were also found at Lanzarote island (Canary Islands) in a volcanic cave.