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"Did you see it? They said it was hauled from the Challenger Deep, but I'm positive that beast never swam in terrestrial waters until a week ago!"
Black Mesa scientist[src]

The Ichthyosaur (taxonomic designation: Xenotherus icthycanthus, or "Spined Alien Fish Beast") is an aquatic alien enemy and mini-boss transported to Earth from the Border World, Xen. Prominently featured in Half-Life and its expansions. It has a small cameo at the start of Half-Life 2.



In Half-Life: Opposing Force, a wall poster depicts the creature's skeleton with the title "Xenotherus Icthycanthus".

Although the in-game creature is named after the extinct marine reptile group, the Ichthyosaurs, it resembles them only in its carnivorous ecology and its general size. When the Ichthyosaur is first encountered in the Half-Life chapter Apprehension, a scientist remarks that while he was told it was hauled from the Challenger Deep in the Pacific Ocean, he believes that the creature never swam in terrestrial waters until a week before. This is possibly the time of its arrival at the Black Mesa Research Facility, the creature being likely from Xen. However, there is evidence that Ichthyosaur specimens were kept for observation, as seen in Opposing Force. It has two arms with one, large sharp claw, a spike behind both arms, and a rhombus shaped tail. In the first game, it is covered in simplistic fins, whereas in the second game, it has feather like quills covering its top, tail, and half its lower bottom. Its head also vaguely resembles that of a chameleon or a frog, with a mouth filled with needle sharp teeth. In the first game, two nostrils are visible on the creature, though in the second game, they are much harder to spot and appear nonexistent. They are also estimated to be about 17.6 feet in length.

In Half-Life, Ichthyosaurs are encountered in several water bodies, including a flooded laboratory, the reservoir near the hydroelectric dam, the sewage areas, and one of Nihilanth's chambers. They are often placid at first, but quickly become hostile, especially should the player take action against them. When killed, they let out a low groan and float to the top of the water. The speed and viciousness of the Ichthyosaur, combined with poor underwater visibility, limited choice of weapons and limited oxygen while underwater, make the underwater areas of Half-Life some of the most frightening parts of the game.

The Ichthyosaur also makes a single appearance in Half-Life 2. During the teleport malfunction ("harmonic reflux"), Gordon Freeman is momentarily transported outside of City 17, in midair. He looks down, and falls into the ocean. Underwater, he is almost swallowed whole by an Ichthyosaur before being transported elsewhere. Although this encounter is scripted, when an Ichthyosaur is spawned using console commands it also attacks the player in the same manner.

Behind the scenes[]

Icky concept

Concept art.

  • The Ichthyosaur was originally referred to as "Muddy."[1]
  • Strong art direction and clear goals were set for the Ichthyosaur from the start, but the AI proved to be very complicated because of the size of the creature and how different it was from the more common game monsters of that time.[1]
  • The Ichthyosaur was to appear more prominently in Half-Life 2, such as in the the Coast levels where it was to fulfill the role of keeping the player from venturing too far into the ocean. However, this was eventually replaced by the Leech. Its only appearance is in the recycled Ravenholm lake seen during the teleportation failure at the start of the game.[2]
  • The Ichthyosaur can be encountered in the playable Half-Life 2 Beta in several coastline maps (such as "d2_coast_02," among others), where it takes the role of the Leech, i.e., keeping the player from venturing too far into the ocean. If the player swims out too far from the land, an Ichthyosaur can be heard and a few seconds after the player dies, while the creature cannot be seen. Interestingly, the Ichthyosaur sounds are named "ping1.wav" and "ping2.wav." This could suggest that the Ichthyosaur detects its prey in a manner similar to sonar.
  • In the WC mappack "marc" folder (referring to series' writer Marc Laidlaw) can be found a map named "ickypop.vmf." Based on an old version of the Ravenholm docks where an Ichthyosaur was to be found, the map consists of a surreal/nonsense sequence: Three Zombies are standing on a wooden bridge in the middle of a small pond. Then an Ichthyosaur jumps from the water and passes above the bridge, killing the Zombies and partially destroying the bridge while doing so. The Ichthyosaur returns to the water, then jumps out of it again and starts flying, excreting gibs while moving higher and higher to the end of the map, to crash in an explosion behind a small cliff. (The creature also does its whale-like sound while crashing.) Above the rocks, right above where the Ichthyosaur has crashed, the G-Man can be seen held in mid-air by a flying crow, who starts fixing his tie in a loop after the creature has crashed. While only the Ichthyosaur's tail can be seen under, it starts eructing an orange gas at the G-Man. The sequence is accompanied by two instrumental tracks, one mysterious (that plays through the all sequence in a loop), another faster-paced (that plays only when the Ichthyosaur first appears), found in the folder "/scripted/stinger/" in the playable Half-Life 2 Beta sound files. They were taken from the Aliens soundtrack (dialogues from the film to be used for the maps "aliens_test" and "testroom_ripley" can also be found in the sound files). After that everything remains the same in a loop. This recalls the scene at the start of the Half-Life 2 chapter Anticitizen One during which the G-Man can be seen on a television screen with a crow on his shoulder. "Ickypop" may be a test map for that sequence.


  • Its name is probably based upon real life Ichthyosaurs, marine reptiles that appeared and flourished during the Mesozoic, and went extinct in the Cretaceous (though it bears little resemblance to the creatures).
  • The auto-aim cannot locate the Ichthyosaur when it is fully submerged if the player is outside the water; however, the Hivehand tracks the Ichthyosaur even underwater.
  • It is possible to lure the Ichthyosaur out of the water in Half Life, specifically at the Dam section. Unlike Earth's fish, it can survive without water and can still chase its prey, albeit with awkward movement.
  • If the Ichthyosaur is killed in Half-Life (GoldSrc version), the player can stand on its body as the body is solid. However, one should avoid jumping on the body if the player falls from a great height as this can injure or kill the player.
  • In Half-Life: Source, it is easier to kill the Ichthyosaur via firearms without entering the water as, unlike in the GoldSrc version, the water has realistic transparency.
  • Due to not having a proper physics model, nor a death animation, they freeze when killed in Half-Life 2.




Half-Life 2[]

List of appearances[]


External links[]