I have no commercial interest in, or personal experience of, this new generation of combined masks and breathing tube(s). As a historian and practitioner of vintage snorkelling, however, I do feel impelled to contribute my 5 cents' worth, based on what I have read about these underwater swimming products so far online and in print.
There has been some correspondence at
https://www.scubaboard.com/community/th ... ks.556777/ on ScubaBoard recently about fatal accidents involving snorkellers in Hawaii.
A couple of these snorkellers wore the new-generation snorkel masks, while the majority did not. To date, there has been no clear verdict declaring that these masks played any part whatsoever in these unfortunate snorkellers' deaths. The jury is still out, and like Grissom of CSI fame, I prefer to "follow the evidence" and wait for definitive proof to be established before passing judgement.
I believe that the first new-generation snorkel mask was developed by Decathlon, whose EasyBreath retail page can be found at
https://www.decathlon.co.uk/easybreath- ... 04664.html. I read everything I could find about this mask while it was under development and I was impressed with the warts-and-all reports Decathon posted to report their progress. If you visit the EasyBreath page you'll notice that the first review is overwhelmingly negative, reporting a personal experience of the nightmare scenario of the mask clinging to the face after the shut-off valves failed to open. On the other hand, every review bar this one is uniformly positive. The Decathlon people, I remember, declared the EasyBreath fit for any kind of snorkelling at first and posted a video of a group of snorkellers happily swimming underwater wearing the mask. Since then, their recommendation has been that the mask should be only used when swimming on the surface of the water. Some manufacturers competing in the snorkel mask market after the initial success of the Decathlon EasyBreath haven't been quite so circumspect about the constraints of the equipment.
And therein lies the difficulty. Only the most discerning customer cares enough about the limitations of what he buys as well as the benefits. We live in an age where the "wow" factor of fast-moving technology blinds and deafens us to the quiet voice telling us that we may need a modicum of knowledge and training, let alone common sense, before we take advantage of whatever happens to be flavour of the month. I once corresponded with a freediving instructor who told me he could teach his students how to do thirty-metre breathhold dives and have them doing so within a single afternoon, which terrified me, while he himself admitted to terror when I told him that I could teach him to hold a basic conversation in a foreign language within the same period!
I'm a great believer in "if it ain't broke, why fix it?" and I always want to know why time and effort should be spent developing a new product and then learning how to use it. The snorkel mask gives the wearer the option of breathing through the nose or through the mouth and I can see the point in allowing for people's personal preferences. The mask does much more than that, however, because it dispenses with the need for a snorkeller to have a mouthpiece stuck in his mouth. This is an important consideration for the minority of people who gag when a foreign object is placed in their mouth for more than a brief time. On Yahoo Answers I once "met" such an individual, who had always wanted to go snorkelling and would have settled for lying on the surface looking downwards if he didn't suffer from a mouthpiece phobia. We also live in an age when people with visible and invisible disabilities rightly want to live as full a life as they possibly can, helped out where necessary with assistive technology. I would say that this snorkel mask might be a real boon to people who can't bear anything in their mouths for very long.