'Whale eye' or 'moon eye,' (I never really heard the term shark eye before) is the term used to depict dogs who are showing the white part of the eye, and yes, you are correct in that it can be seen in situations of stress or aggression.
A classic example is a dog who is guarding a bone. The dog has his head lowered over the bone but he may be looking slightly sideways to make sure nobody comes near, and the whites of the eyes may be showing.
The third eyelid showing is a different situation. This involves a different part of the eye which is the third eyelid which resides in the inner corner of the eye when the dog is alert and awake, but slides over the eye when the dog falls asleep or when the dog is feeling unwell or there is some neurological dysfunction.