Can mobs not spawn on water?

[ZitMa]

I'm trying to make a mob farm where they spawn on water and it pushes them. I'm doing this with pigs. But they don't seem to be able to spawn on water, even with grass under it. Maybe it's because I put the spawner on the ground, but I don't know if passive mobs can spawn on water.

 

[ned_]

It works for me..
the problem is you put the spawner on the ground or because of the server hardware
Well one way to fix it is redo the spawner thing that uses water or make a new one or make a new island
mobs like blazes, zombies, pigman must spawn on a dark place (no lights)