Place the pork roast and water in the crock pot. Cover the crock pot and cook on low heat for 4-6 hours or until the meat is fork tender. Remove the pork from the crock pot and place on a platter or large cutting board. Let cool slightly then remove any visible fat and shred the pork using two forks. Return the shredded pork to the crock pot and add the barbecue sauce. Stir well to coat the meat in the sauce. Cover the crock pot and cook for 30-45 more minutes or until the sauce is heated through. Serve the shredded pork on buns or in tortillas.