Nemopsis bachei is a species of relatively small gelatinous zooplankton hydrozoa found in both marine and estuarine environments.

[1] As part of the phylum Cnidaria they are mainly gelatinous with their most identifying characteristic being the gonads which, viewed from above, look like an X and then continue down the sides lining up with the radial canals.

As a part of the zooplankton, it is incapable of sustained horizontal movement and relies on its tentacles to encounter and capture smaller organisms for food (feeds mainly on copepedites, selecting against naupilar stages).

While they do consume a substantial amount of zooplankton when at peak abundance, due to the regeneration rate of copepidite stocks, N. bachei were not found to have a lasting effect on the overall population.

[3][9] It has been documented as native to the eastern coast of the US and the Gulf of Mexico and recently has been found to be an invasive species in the coastal waters of Northern Europe.