I love shrimp for live.
My favorite for specks is a top water popper with the rear treble removed and a 18" leader attached which has a jig and plastic attached. You get to cover the top and subsurface at the same time.
How deep of water?
Where ever I fish them. It seems I'm mostly in the 4-12 foot depths. If you've ever used live bait behind a popping cork you'll get lots of hits at the cork, which is why I like to use a plug. I'll generally start with live and then when I find a bunch I'll switch to the plug and jig.
I love it when they hit top
