The Cerathecan (Exile cerathecan, “the horn-cupped exile”) is one of Subnautica 2’s genuine biological mysteries. It is, genetically, still a large shrimp — yet it pilots a double-valved shell its genome contains no genes to produce. Where the shell comes from is an unanswered lore thread.
It steers the shell via a central eye and periscopic ears, feeding with basal tentacles. The shell interior holds a paralytic neurotoxin that subdues struggling prey. It grazes detritus when calm but hunts on sight and becomes markedly more aggressive when hungry.
Counterplay: it is durable (≈1,000 HP) and high-bulk, so it can shove you around. Engage with knives, harpoons or vehicle tools rather than trying to tank it, and disengage if it is in a hunting state — a hungry Cerathecan does not give up easily.