It would be possible for them to get through the locks but not often. They would just be lucky to come in when the gates are open and lock up with a towboat. Possible but not probable
But during very high water when the dams are open river and all the gates are out of the water they could just swim through. Since they have made it up the Mississippi to Illinois, I am sure they are in the Arkansas.
The reason for this question told a freind of mine not to swim in the river below the Toad Suck dam in Conway because there were bull sharks there. I was just curious.
We swim in the Arkansas River south of Toad Suck just about every weekend. If you want to find us look straight across from the fouche river on the sand bar and there we will be. We have done this since about 1995 and I hate to report no sharks ;)
have any of you guys ever seen the show River Monsters? there's a good possibility that they are in there but i dont think id worry too much about it. you'd have better odds winning the lotto than getting bit by a shark in the AR river