Zombies don't have working lungs, so there's no air in their lungs, therefore no, they do not float good sir.

But the zombies will eventually bloat up and float to the surface.

if they bloat up with water, water is not lighter than water so they would not float for that reason.

that's not the reason. Dead bodies still float

Go into a pool, let all of the air out of your lungs, and see if you float.

At this point we are both stating facts.

A person can make himself sink, and a dead body can float

kk. I know this because science. A dead person floats because the decayed organs release gasses internally. However, a dead person with holes in it will not float. If they cant digest food they wont survive though so unless they learn how to swim they cant cross water.

all people float, dumbass.

that is true. But my question is why people think a moat can stop zombies