"Seeing a moving picture in HD isn't exact enough" and other silly thoughts.
At any given moment, you can more or less guarantee that being able to see a livestream of a location will give you enough information to teleport to it.
All that is required is a clear, mental image to teleport.
You want to teleport to that field of grass, so you focus on the picture - how every blade is moving, how the BBEG's footprints leave the blades depressed, that patch of grass that is a little darker green than the rest. That particular glade, at that particular moment, is going to be unique in it's appearance, and if you can't garner enough information in 20 minutes of observing it,
you aren't smart enough to be a wizard.
The same thing can be said of the water scenario. Depth of color, varieties in color, frequency and strength of waves, ripples, splashes, and a whole host of other observations will merit a unique location at that point in time.
If he's swimming, you cast Fly, teleport on top of him, and give him the old Shivering Touch, maybe throw a Forcecage around him, use some of those Iron Bands of Bilaro we've been talking about, Wrack, Freeze Armor, or any dozens of ways to immobilize him (remember, saving throws can be more or less negated with a Moment of Prescience) then watch him drown.
If he's sleeping, you just teleport in and let your 2h Fighter CDG him.
There is a rather large list of Save-Or-Suck spells that can target just about any weakness, and more or less guarantee you or your party can end an enemy before it has a chance to recover.
I think the core of the misunderstanding issue is that you haven't ever had a Wizard who knows how to break games on your hands.