Like the man said, when people refer to the 'Basin' they're referring to the Atchafalaya Basin. There are many places to launch a boat at public ramps. Academy, Spillway Sportsman and others sell maps; some black and white, others in color. Knowing where to go takes time, patience or a good heads-up by fellow fishermen. Drop me an email and I'll try to point you in the right direction.
I'll add to the other 2 post by saying that if you are familiar with Henderson, it is in the 'basin', however there is a levee between Henderson and the rest of the basin. That's why there is a water level difference between them. The water can be low in Henderson and high in the basin. I launch at a place called 'Upper Grand River Launch. If you type it in on google earth you will see it. The basin is so big that if 100 people showed you around, you would see 100 new spots. I would show you, but I don't freshwater fish. Come hunting season holla, and I can bring you out there and show you some cool stuff.
ok let me try to help you the basin that everone talks about is the Atchafalaya Basin that goes a long way i know the part that runs from I10 to morgan city there is a lot of places to put in at i use the ramp a pigeon thats down below plaquemine and you launch into the atchafalya river and go south everthing on your right is the basin there is a lot of places in there to fish for what you want if you would like we can make a trip together one day i need a fishing buddy i have a boat and i wouldn't mind showing you where to go i don't think you will catch them all. let me know if this helps. you can email me jbouillion@cox.net