As mentioned, some very specialized equipment is needed to scout and hunt in shallow backwaters and on large rivers and reservoirs. A shallow-draft johnboat (must have a semi-V bow) is the ticket for hunting in thin water, and a long-shaft, direct-drive motor (Go-Devil, Mud Buddy, etc.) will plow through shallows and brush where an outboard is worthless. A portable blind on the boat is a nice extra but not a necessity.
Also, an ATV can be handy for running off-road trails, and a good pair of waders, a hiking staff, and a backpack will provide walk-in access to hard-to-reach hunting spots. A 4-wheel-drive pickup or SUV will allow boat launching on unimproved ramps.
A larger, deeper boat is necessary for running big water. High waves and strong currents can be dangerous, and a deserted stretch of river is no place to find trouble. Also, an outboard with enough power/speed to cover long distances on rivers and lakes is advisable. Sometimes you will have to run several miles before locating a spot where waterfowl are working.
A topographic map is indispensable in looking for new hunting places. I maintain an extensive map library. If I identify a new potential hunting spot, the first thing I do is obtain a topo map that covers it. Having good geographical references is vital in scouting, especially for figuring out how to get into an area.
Also, a GPS (global positioning system) unit makes navigation a snap. By marking and following GPS waypoints, you can weave your way through a swamp with confidence.
For those who can bear the expense, flying is one of the absolute best ways to scout for waterfowl spots. You will spy places you never imagined existed. When you identify an area for scouting, you can hire a small plane and pilot and check it from the air, looking for potholes, sloughs, openings in green timber, etc. You can also figure out the best way to get into these places. Be sure to take your map with you on the flight, and mark it so you can follow up with an on-ground exploration. Truly, an hour or two in a small charter plane will pay long-term dividends in waterfowl hunting pleasures.