Our latest example of undersea horror is clearly the inspiration for last year's eco-horror mockumentary The Bay. The central monster of that film was a species of prehistoric marine parasite that first fed on the tongues and then all of the internal organs of fish in Chesapeake Bay, before moving on to larger hosts... and by “larger,” we mean "us." While there haven't been any reports of the species cymothoa exigua, or “tongue-eating louse,” feeding on anything besides specific kinds of fish, the similarities are hard to ignore. Seriously, watch this clip from The Bay and see for yourself.
This tiny terror is small enough to enter the gills of a host fish and latch onto its tongue, which is then drained of blood... but that's just the beginning of the nightmare: the tongue eventually dies, but the fish lives on, with the louse actually taking the place of the tongue. Scientists have not found any other examples in nature of a parasite replacing a host organ and actually taking over that organ's job.
You may rest a little easier knowing that cymothoa exigua is supposedly harmless to humans. But just imagine the body-horror possibilities if this little guy suddenly develops a taste for your taste-buds...