That really depends on the shoe though. I have two pairs of paddling shoes, one is a Tevas brand and it is very thin and flexible and sole is simply a real thin band of nylon with a rubberized sole for traction on it, it's really flexible to one's feet, kind of like say a ballet shoe. But the other shoe I have is heavier, beefier and has a more serious sole. You can squeeze the heel and toe between your hands and it will resist where as the Tevas I have would practically crush into a ball. You can find some paddling shoes that are beefier though, so keep that in mind.
The one paddling shoe that I do wear for walking is made by Merrill, which also makes the trail runners I have (red slate desert). I live on a lake community and I'm about 3/4 mile from the lake via roads, a trail, and a fireroad. I've used the Merrill paddling shoes and they are comfy to hike in for short distances. You mentioned water crossings, surely you would change off to your hiking boots/shoes after the crossing, right?
Jay