Snake does speak English, but he could only guess at that being the question, as sound does not travel well between air and water, but he'd seen enough people speaking outside his tank that he had learned to catch a few words.

He had been too scared to speak with anyone, though. Abuse was not the kind of thing that inclines someone to speak with their captors. No one else had given him reason either, and while this man is clearly a little different, he wasn't sure just how.

He does wake up a bit more, his tail flicking as he pulls away from the front of the tank, skeptically looking over the man from the shadows. Even if he keeps his mouth closed, there's an obvious intelligence in his eyes as he watches the stranger to see what he's planning. He does give Joker a bit of something, though, tilting his ear more towards him and then looking up to bring Joker's attention to how he had no room to surface in his tank.