Can spiders swim against current?

In Minecraft 1.4_01 if I have a vertical wall standing on dirt with a water source block placed where the wall and ground meet (see below) can spiders (or any mob for that matter) even reach the wall?

C = Cobblestone
D = Dirt
W = Water Source

C
C
C
C
CW
DDDDDDDDDDDDDDD

For the sake of simplicity I've intentionally not listed flowing water.


At the moment, mobs cannot move fast enough to fight a current. However, this is rumored to change in a later patch.