AS the owner of 5 turtles for a long time I will be the first to blast you and ask WHY you took it from the wild? This was not yours to take and with all of the captive bred specimens available this is no longer necessary. You probably took it in, and if you did what most people do, not know enough on how to take care of it thus it is now sick and NEEDS TO SEE A VET!! Swimming lopsided is a sign of pneumonia or respiratory disease which can be brought on by stress (being taken from the wild) Get this guy to the vet and once it is better set it free and get a captive bred instead. Keep the temps up in the meantime as stated on the other post.