Here in Texas we call it grappling. You get into a river...that is you walk into the river...usually alongside the high bank of the river or creek. As you walk in the water you use your feet and hands to 'feel' the bank for a recess or little wallowed-out concavity...or you feel in a log, or under a beaver dam. This is where large catfish hang out. Once you feel them you get their orientation and put your hand in their mouth and try to grab the lower jaw and once you have a good hold, you pull him up. Some people will thread a rope through the mought and out the opposite side of the operculum and then they have the fish (if they hold on to the rope). Noodling is catfishing. The confusion arises when you feel a 100 pound alligator snapping turtle as he closes his jaw down on you arm or fingers. They say a beaver is very disliked among the noodling croud. Water moccacin are often spoken of, but they do not generally lay under water for extended periods of time, so it is only the occasional noodler who get invenomated by that viper.
Noodling is destined to become popular with an active noodler in the Old Executive Office building.