Like Subs? Like Planes?

[Oberon]

Looks quite plausible, although I should imagine that there would be a fair bit of drag both underwater and in the sky, and with those windows it wouldn't be able to take much of a battering by enemy depth charges....still a very cool idea...perhaps it has a civilian usage in this day and age? A quick flight out to the reef and then a submerged tour before returning.