The swimming wouldn't even need to be of going underwater. Just you know, being able to move past ankle/knee-deep water. :S Those invisible walls drive me nuts. And the fact that to swim, you have to sit. Like... Who sits in a swimming pool or a hot spring? Well, I guess some do, but you know what I mean...

Back in beta I was hoping that you could slip and die in Tam-Tara for moving too far, but the walls made sure you didn't have any risk. Not to mention it'd be funny on WHM to knockback mobs into the abyss.