One of my favorite classes to teach is the PADI Rescue Diver course. While in-water rescue is serious business, the class is fun both for me and the students. It is frequently the first time diver begin to shift their focus from themselves and develop situational awareness. The comfort level with respect to their own diving, from the beginning of the class to the end, is remarkable.
A central skill during the course is in-water rescue breathing. It’s tough for a number of reasons, but one major challenge is maintaining and open airway to administer breaths without pushing the victims head underwater. The article linked above addresses this issue.