So, at the end of Civil War, Cap breaks into the Raft and rescues his imprisoned comrades Falcon, Hawkeye, Ant-Man, and Wanda Maximoff. How did Cap pull this off though? The Raft is in the middle of the ocean, and is kept submerged when people aren't going in and out. Furthermore, the Raft is designed to hold enhanced and superpowered individuals, likely up to and including the likes of the Hulk. Security would definitely be tight there. Not to mention Cap's one of the most wanted fugitives in the world, so any sign of him in the prison would probably lead to a complete lockdown. Finally, Cap has no shield at this point in time, and we do see that the Raft's guards are armed with guns. How would he protect himself against bullets without his shield? This is made even more difficult by the fact that Cap almost certainly would not be willing to kill innocent guards to break out the arrested Avengers.

So, Cap probably had help. The person (or people) who helped him would need to be able to reach the Raft out in the ocean, be able to circumvent any security systems placed in their way, and would not be stopped by bullets. Cap was last seen in Wakanda, so perhaps T'Challa helped him? The Black Panther would be able to reach the Raft, because he has his own aircraft, and his vibranium suit is bulletproof. However, he'd still be stymied by the security systems, and the king of Wakanda going on a prison break in a UN facility would probably lead to unwanted political consequences. So T'Challa is probably out.

What about Vision then? Vision can fly to the prison, and phase through any security systems they put in his way. He can also either let bullets phase through him, or simply allow them to bounce off. Therefore, if Cap had help in his prison break, then it most likely came from Vision. Cap could've waited on a nearby boat or airplane, allowed Vision to go in first to take down security, and then gone in after the coast was clear.

Why would Vision help? Well, Wanda was being held in there, and he probably wouldn't like that.