Earl Williams, aka "Swamp Thing", is a convict in Con Air. He is one of the prisoners from Carson City, and revealed to be Cyrus "The Virus" Grissom's designated pilot. Swamp Thing is portrayed by M.C. Gainey.
Swamp Thing appears when the Jailbird lands in Carson City, he is one of the first convicts to be shown. As he is loaded on the Jailbird, he enters the cockpit, removes the transponder, and gives it to Pinball, who then sneaks out from under the Jailbird, hides in plain sight, and puts the transponder into another plane. As soon as Cyrus kills Starkey, they get ready to take off. The radio tower person says they are not clear for takeoff, but Swamp Thing just laughs at them with a vulgar joke, while taking off. Francisco Cindino asks if the Jailbird can be tracked, which Swamp Thing confirms so, only for Diamond Dog and Cyrus to notice the transponder missing, much to Cindino's relief.
As they arrive in Lerner Airfield, Swamp Thing almost collides with another airplane, causing him to almost crash into a giant fuel tank. When the convicts step out, Cyrus decides that they dig out the Jailbird. While they are digging, Johnny 23 spots the military coming, causing them to dig faster. In the commotion, Cindino's plane tries to take off, but the plane's tail is knocked off by a crane used by Vince Larkin. When Cindino pleads that he was coming to get them, Cyrus doesn't buy it, taking Swamp Thing's cigarette out of his mouth, and tosses it onto the spilled fuel, engulfing Cindino in flames, killing him. When Cyrus orders the cons to fight the military, Swamp Thing is forced to get the Jailbird ready by himself.
As the Jailbird is in pursuit by the army helicopters, Poe makes his way towards the cockpit, ordering Swamp Thing to land. Swamp Thing tells him that their plane is low on fuel, one engine is not working, and they are dropping too fast, expecting to crash.
The Jailbird crashes into Las Vegas, and Swamp Thing, Diamond Dog, and Cyrus the Virus steal a fire engine, and are pursued by Larkin and Poe. Diamond Dog tries to shoot the pursuers, but Poe's motorcycle crashes into him, causing the motorcycle to explode and killing him. While Poe is fighting Cyrus, Larkin orders Swamp Thing to pull over, only for Swamp Thing to respond by swerving. Larkin then grabs a fire hose, and uses it to get Swamp Thing to stop, flooding the cab. This causes Swamp Thing to jump through the front windshield, causing the fire engine to run over him, killing him.
Swamp Thing is shown to be very knowledgeable when it comes to vehicles, whether it is flying a plane or driving a fire engine. He also knows how to remove a transponder, and attach a battery to it, so it can work without being attached to the plane. Despite working for Cyrus, he comes off as a nice guy (like Pinball), such as when Poe takes over the plane, Swamp Thing simply obeys him rather than question him, even though they have different goals for the plane. Of all the convicts, Swamp Thing is the most loyal to Cyrus, having no desire to betray him (unlike Cindino and Diamond Dog), nor does he hate him (unlike Johnny 23) or fear him (unlike Billy Bedlam). He also doesn't tolerate betrayal, as he is clearly furious that Cindino had tried to abandon them.