What day did the media first report the balloon? In an interview today Biden said that he ordered it to be shot down on Wednesday, and the military made the decision to wait until they thought it could be done safely, which apparently was 3 days later. I think they should have shot it down as soon as it crossed into US territory. Most of Alaska would be unpopulated enough that they could drop it almost anywhere. Then it flew over Canada so it was their responsibility. Then as soon as it crossed into Montana it was probably again over a sparsely populated area.
I'm a layperson in all fields relating to this situation, so this is just my speculation and perspective:
Presuming this was intentionally sent over our territory (and, I am presuming it was), I believe the thing was sent more to see what our reaction would be to it, than for any actual intel it gathered. I believe showing a measured reaction to something that was certainly not a threat is a better reaction than a hothead guns blazing response.
I also believe all this stuff the media is fed about "Biden wanted it shot down sooner and he listened to military folks to wait until it was over water" is just pablum. I'm sure as soon as the this thing was noticed (before it was over us) and they determined it was likely to overfly us, a complete response decision map was laid out and everybody probably agreed to it. Of course, the President has to assume a tough posture so he gets to say he wanted it shot down posthaste. Fine, whatever, this is theater leaders (of either party) do.
That all said, this thing wasn't a threat to us and I'm pleased we didn't react to it with kneejerk hawkism.
About it being in the water and how long it takes to get to it:
Reports said the area where it went down was secured so no amateurs are going anywhere near it. Remember, the payload structure was 3 schoolbusses long... that's what, maybe 80 feet? For all we know it landed on end and could be sticking out of the water. But where it went down remnants of the cables/balloon material certainly would be at or near the surface. They certainly know where the thing is, to within a coupled dozen yards. I'd be shocked if they didn't have a buoy attached to it within an hour of it splashing down. Wait for the right equipment for extraction, but they know exactly where it is.