This happened in Roatan with a combined group from Jewel and Harmony of the Seas, so I figured I would share with everyone as a lesson and urge those with some experience to continue in your education. For anyone wondering I am PADI Rescue certified.
I was buddied with an older woman who was open water certified, as we were both traveling alone. The first dive she was cold to the point where I saw her hand visibly shaking so I got her out of the water asap. She rented a wetsuit and they added a few extra pounds. The second dive maximum depth was 60 feet and we were dropping in right near the edge of the reef. I started my decent and leveled off near the top of the wall around 50 feet with the rest of the group and checked my buddies position she was a couple feet away near the dive master in a vertical position watching her console and equalizing. She was a few feet behind the edge of the wall and continued descending. She had froze and was fixated. The dive master and guide were making noise and she would look up but could not see through her bubbles. Once I realized she was not stopping I began to descend with her. She was about 15 feet below me when she finally hit the bottom at 100 feet... thankfully we were not over the area where it drops to 300 to 1000+ feet. I again signaled for her to come up and she acted as if she was stunned and just stood there. I descended to her and she showed me her console. She never added a single whisper of air to her bcd.
I tucked her console into her bcd under her arm and added a little air to mine and grabbed her inflator with my left hand and her cylinder valve with my right and began to add air to her bcd until we began to rise. I swam upwards towing her and along with me until we got to 50 around feet and rejoined the group. The dive master and guide had stayed behind with the main group. Our accent was pretty much uneventful and I got her leveled off and stabilized with a neutral buoyancy and we completed the dive.
It still gives me chills to think what would have happened if she was over deep water and I had not been there. I know I would have dumped my air and hauled ass to get to her but if I hadn't been there she would have likely been lost...
She was open water certified and claimed that she stopped counting after 50 dives. She was overconfident in her skills even after freezing up and requiring someone to come get her. And insisted that she didn't need to get any more training.
Even if you are only diving a couple times each year achieving rescue diver is an admirable goal as it will also help you keep your head in a potentially bad situation. I always want every person who goes into the water for a dive to come home safe and sound even if you are not diving with me.