Following distant sound, zombies roam the abandoned land. They smash houses, and bash down trees, and destroy cars with their flesh arms – some are blown away by explosion, but more move on – but now they come to the bank of river.
One by one they jump into the water, like migrating zebra. Unlike living animal, they cannot swim and just sink to the bottom. Submerged zombies lose track of the sound on land, and aimlessly move underwater.
Thus, river and sea gradually collect all zombies.