Tailwaters are the waters directly below dams, and these can be excellent places to fish. Many kinds of fish run up rivers to spawn and are stopped by the dam, piling them up in a small area in the tailwater. Water coming from the dam also digs deep holes below them, offering fish a place to hold. Some dams have fishing piers on them for access to the tailwaters and others allow bank access.
Water can rise rapidly below dams when power generation is started or water is released for some other reason. Be extremely careful when fishing below dams and watch for rising water. Make sure you can get to safe ground quickly.
Visit dams on lakes near you and check for access below them. Some have piers, some have parks with bank access, and some have paths you can walk down to get to the water. Be careful when going to the water and make sure you're allowed to fish there.
When you fish below dams you will face strong currents so you will need lots of sinkers to get your bait down to the fish. If fishing for bottom-feeding species like catfish, a fish finder rig works well. Try to find eddies to fish because many kinds of fish like to hold in slower water and wait on the current to bring food to them.
Big catfish are often caught below dams and you will need heavy tackle for them. Walleye also hold below dams and feed there, but you need to concentrate on slower water behind wing dams built to slow the current and rocks around them. Striped bass run up rivers to spawn, and you can even catch saltwater stripers if you fish below the last dam on a river. Landlocked stripers and hybrids also run up rivers to dams above lakes.
Smaller dams can also offer good fishing in their tailwaters. Big bream and cats often hold below pond dams if the creek or stream is big enough for them. Bass can also be caught in the creeks below pond dams. Sometimes a pond dam near a public road will give you access to bank fishing near it, but most times these smaller dams are private and you'll have to get permission to fish them.
Many cities and towns have water-supply lakes that are closed to fishing. Check to see if you're allowed to fish below the dams on these lakes since you won't be fishing on the lake itself and won't be affecting the drinking water.