To dream of a stingray represents an aspect of yourself that passively accepts itself as dangerous. Feeling that something could be dangerous at any time, but isn't right now. Feeling that a passive situation or person has the potential to be lethal.
Alternatively, a stingray could reflect feeling about "sting" operation. Passivity that could strike at any time.
Example: A young woman once dreamed about a stingray. In real life she felt intense regret for having cheated on her ex-boyfriend that she believed hated her. The stingray in this case may have reflected her feelings about talking to her ex being an emotionally dangerous because he might remind her of her cheating at any time.
Example 2: A woman dreamed of seeing a stingray. In waking life she was concerned that her boyfriend writing letters to his ex-girlfriend over a child could potentially lead to cheating possibly ending her relationship. The stingray in this case may have reflected her feelings about the potential cheating being passively dangerous to her relationship.