Divers are a way to get your fishing gear down to the desired depth by letting the current do the work. This allows you to take lures and rigs which normally would have to be casted and retrieved, and then fish them like you would a plug.
I think this is a great technique for those times you need to be especially stealthy.
There are a few different kinds of divers. Jet Divers are popular choices and come in different sizes.
Another choice is the Mud Divers made by Brads. These look like plugs, but are painted black. The bill is also a bit bigger and made of metal. In fact I know one guide that simply buys plugs on sell, removes the hooks and then spray paints them black.
Rigging it up is pretty easy. Attach your line to the snap on the bill.
Then take your tackle, put it on a leader and then tie the leader onto the belly swivel.
People usually call them bait divers because bait, like roe or shrimp, is common thing to use with divers. The setup is similar to plunking, only attached to the diver instead of a big weight and spreader bar.
Another one of my favorites, especially when the water is low, is to use a long leader and a small dick nite spoon.
You can fish them much in the same way as fishing plugs – on anchor, back trolling or forward trolling.
For more information about coho fishing check out this page.