RC,
I know that you have more experience in these matters than I do, but historically, I have never heard of divers being brought in unless there were indications that someone could be in the body of water.
Even when there is a highly suspected drowning, they usually drag first, then send in divers, which is just the reverse of what they should be doing! I am a SCUBA Diver, and dragging would stir up all kinds of muck, not to mention possibly screw up any evidence that might be visible, by the time they are finished with that, divers are working by feel, cause they could not see their hands in front of their masks with all the mud and slit being moved around.
I was at JJ today and met several of the sleuthers, this was the first I had heard about divers in the water at all, and IMO that was early, and not in a spot that I would have expected them to be looking, given her proclivities for running around Regency Park, which also has a fairly large body of water.
CyberPro