Several early maps are known to feature the Hydra, and can be found in the WC map pack and the playable Half-Life 2 leak. It is also reminiscent of the real-life hydra, an invertebrate freshwater animal, notably a transparent body, and the Ancient Greek serpent-like chthonic water beast that possessed 9 heads, Half-Life 2’s Hydra also having several heads. The Hydra's design bears similarities to the Tentacle from the original Half-Life.
The only real model animations are when it is idle and when it strikes, as well as the scripted animations for the E3 demo. The deployment, left and right movements of the Hydra are completely controlled by the game code. It was to be met during the City 17 uprising, in and above the underground sections set between Alyx's kidnapping and Barney's rescue from the Overwatch Sniper. Its body was to be made of gelatinous, transparent flesh, with organs clearly visible.
Each tentacle was to end with a different 'head'. The Hydra was to be a massive colonial organism made out of three neon blue tentacles that went up to the surface.
