Sharks stranded and killed by the receding flood, their corpse markers littering Carl's map on ring nine.
By the time Carl's party reaches the ninth ring of Larracos, it is clear this is the area they were in before, and that it was flooded until very recently. The ground remains wet and slimy, and the Xs of dead sharks litter Carl's map.
They are the counterpart to the jellyfish still closing the Piccadilly Theater's balcony: leftover sea life that came in with the Flooding and died when the water was drained down to level 3. The corpses sit among bars, saferooms and cleanup crews as the awakened city scrubs itself down for the coming war.
Corpse markers scattered across the map of a wet, slimy ring, the animals stranded when the water dropped.
Physical evidence of how deep and how recently the sea filled Larracos's lower rings.