it has much greater physiological effects than those of a snorkeling so if they said SCUBA it would make more sense to me.

I'll tell you my thoughts and I think I am pretty close on this due to that experience. First, if it is a full face mask it probably is one of those really cheap ones where you breath in and out the tube. That is the worst thing you can do because it does end up greatly increasing your CO2 level. Even if they use the single snorkel, most of those are cheap and are the same thing. If you have a cheap snorkel do not breath out your mouth, breath out your nose so the co2 goes out the mask and you only get fresh air through the snorkel. If you have the low end purge (next to the mouth piece) it's not bad because most the co2 goes out the purge valves but still is better to breath out the nose as the purge valves are mostly for expelling water after you fully submerge and come back up. However, most people don't like to breath out the nose because they are unable to keep the mask from fogging so they continue to breath out the mouth. If you want the cheap island recipe that many of us use when we don't have a fog stick, ask a local about the sea naupaka plant. They are all over the beaches. I digress, I feel their breathing technique is most likely the biggest culprit in these drownings. By the time they realize it they are so groggy and disoriented they drown. Add to that, age and weight problems as well as other comorbidities and you have a simple recipe for a tragedy. Especially for people not used to swimming in the ocean where you have to fight waves and a lot of times strong currents. These people should stick to places like Hanauma Bay or close to beaches at low tide. And it wouldn't hurt if they had some instruction before they donned the mask. So I would actually chock it up to inexperience with a potentially deadly activity. I think the quote "Lack of experience in the water was not a factor for getting into trouble either." is misleading and very bad. Sure everyone has been in a pool or a lake or even the ocean, but doing it with a mask and snorkel is different. Especially in the ocean in Hawaii.

As for the article, it's pretty lame. It basically says we have little data to go on but we do know if they were snorkeling or not.