This looks so impractical on so many levels.
Wet suits for the riders? Capacity goes waaaaay down, operating costs go waaaay up.
Strapping somebody down and then submerging them under water seems like a really quick way to induce panic attacks. And with the restrains and that canopy over their heads, the passengers are screwed in case an emergency occurs.
Is air pressure the only thing keeping the water out? Creating a bubble the same way holding a glass upside down in a basin of water? Then you're really dependent on that canopy staying air tight. Daily inspections of all those seals would be required, possibly daily pressure testing as well.
Not sure how deep into the water the ride goes, but you'd also get some funny effects of sudden transitions to high air pressure. A couple of meters down, and the difference in air pressure would be the same as that between sea level and high-altitude air liners. Your ears would feel funny. And if something is meant to seal between the cabin air and the water (to keep cabin pressure nice and comfortable), good luck getting it watertight around the bodies of the riders.
And what if an E-stop occurs, or riders otherwise get stranded? Better pack some spare air (and that requires a whole new set of certifications and training for the ride and all crew), but you'd also have the more pressing problem of removing excess CO2 from the vehicles. In an airtight space, CO2 poisoning from your exhalation would kill you long before oxygen depletion sets in. In other words, you need a system that actively circulates air from the cabin, and one that provides fresh air. Both would have to be pressurized. And work under water. And of course, stranded riders would probably be fine with stopping for about twenty seconds before the screaming starts.
In short, this looks like it combines the worst parts of scuba diving with the worst parts of submarines. There's a reason why Disney's 20,000 Leagues Under The Sea were not completely submerged, but were more like boats that ran really low in the water. They didn't have to deal with air pressure, and there was always a quick and dry escape to open air.
It'd be interesting to see how they solve the logistics problems if they ever get this thing open, but I'm not holding my breath for it. And I can't imagine it ever being profitable.
