The mysids are similar to krill or small shrimps or in appearance and size, but are only distantly related to them. The main thing that sets them apart is some kind of pouch under the female body where they store the eggs. In zooplankton samples, they are also more grey in colour than the lighter coloured krill.
Like krill, the mysids are relatively good swimmers and are often found in the water column. However, they are often found on the ocean bottom as well. It is not clear-cut if they should be classified as benthos or plankton. Mysids are fairly common around Iceland, but have not been studied much besides ad a food for fishes.