The Swimming Alien was a large Xenomorph that was at least primarily aquatic and was encountered by USCMC personnel on Bracken's World. They were most likely spawned from the planet's native large achelate crustaceans.


All Xenomorphs can swim, but since these Xenomorphs have no legs and only a lobster-like tail fan and three pairs of pleopods (swimming legs) to propel them, it can be said they swim better than their terrestrial cousins.


The upper half of the Swimming Alien's body was much like a standard Xenomorph other than its webbed hands, but the lower half of its body formed a large tail featuring a lobster-like tail fan instead of legs. The tail had three pairs of pleopods (swimming legs), though whether or not they were also capable of assisting with terrestrial locomotion was unclear.

The Swimmer possessed a dark mesoskeleton with a blue hue, much like a lot of other common Xenomorph castes. The Swimming Alien has shorter dorsal tubes than the typical alien (excluding the Runner which has no tubes at all), similar in proportion to the Arachnoid. They also possessed thin tendrils hanging off the side of the lower jaw, much like a Queen Mother but not as long.

It is possible that the aquatic Xenomorph is a type of Praetorian due to its large size and crested head, though because they are so numerous and only seen as attacking rather than defending territory, this could simply be the result of the Xenomorph DNA reflex adapting features from a large host species, or possibly even genetic modification. The latter option is further supported by the particular rarity of transbreed Praetorians.



  • The Aqua Alien is another Aquatic Xenomorph.