The Shockirus first attacked the fishing boat the Yahata-Maru, after the vessel came dangerously close to Godzilla. The sea louse was succesful in its attack, slaughtering ten of the crew members, and leaving behind only one survivor: Okamura.
A short time later, news reporter Goro stumbles upon the Yahata-Maru, adrift at sea, and boards it in an attempt to locate the crew. Upon finding the deceased crew members, who were sucked dry by Shockirus, Goro himself is attacked by the sea louse. The creature manages to pin Goro down, moving in for the kill, until Okamura comes out of hiding and buries a hatchet into the creature's back, killing the Shockirus.
Shockirus appears in the Dark Horse Godzilla comics where it attacks Kino and Take' when they climb up Godzilla. A creature ressembling Shockirus appears very briefly in IDW's Rulers of Earth.
Shockirus are extraordinary jumpers, and also can suck vital fluids out of a host. Their hard carapace also protects them from harm.