It’s the question we’ve all been asking ourselves since it was announced that the second season of Fear the Walking Dead would take place, in part, on the sea, but now we definitely know the answer to the question:
Can zombies swim?
Kind of. I don’t think Olympic swimmers have anything to be concerned out. The zombies’ ability to “swim” can best be described as a lumbering while floating. It’s a frightening sight, to be sure, but not a particularly lethal one because escaping a swimming zombie is basically like escaping a floating volleyball. I suppose that, if one were surrounded on all sides by swimming zombies and also couldn’t swim, floating zombies might pose an actual threat, but otherwise, they seem to be even less menacing than the largely decomposed land zombies of The Walking Dead.
The bigger question, from a scientific perspective, is this: Should zombies be able to swim?
The answer to that question is yes and no. Zombies are essentially cadavers that can still move, so their buoyancy correlates with that of a corpse. Corpses do float for a brief time, but only until their lungs fill with water. Once their lungs fill, a dead body will sink, as we saw with the body of Lisa Ortiz in the second season premiere. When her son tossed her over, Lisa sunk straight to the bottom.
Zombies will continue to sink (or lie on the bottom) until the bacteria in their guts produces enough decomposition gasses — methane, hydrogen sulfide, and carbon dioxide — to cause the cadavers to float back to the surface. This typically takes days to weeks.
In other words, zombies should be able to float for a few minutes and then again several days or weeks later, after bacteria have produced enough decomposition gasses. In this case of tonight’s episode, the zombie with the life jacket checks out, and the zombie trapped underneath the wreckage checks out. However, he zombie from the nearby wreckage at the end of the episode who was floating above Nick probably shouldn’t be able to float because it had been dead long enough to sink and not dead long enough to float back up during decomposition. That is, assuming, the zombie in question did not float from elsewhere.
All of which is to say, the science doesn’t check out on one zombie, and as we all know, Fear the Walking Dead is all about being accurate with the science of zombies.