"I've heard that a petroleum company has a tubular-platform plunging down over a mile beneath the surface in the Gulf of Mexico.
The pressure at the base of that tubular platform is around
160 x 14.7PSI. That's just under 2,400PSI.
I'm told that water, under such pressures, would literally
"explode" if thrust into a low-pressure environment."

Hmm. I've seen the Discovery channel show on the Troll with guys working near the bottom of ocean- but it's not mile down- less than 1/4 mile. I believe their concrete walls were around 6' thick- but the diameter was pretty big- easily fit a basketball court in there.
I haven't heard about this thing in Gulf of Mexico- I'm surprised there is any water in the Gulf which is a mile deep.
A mile under water is a pretty harsh environment. I'll remind people that IF there was a pipelauncher which exceeded a mile in length, that even though part of pipelauncher was below a mile- this huge pressure wouldn't be much of a factor. A pipelauncher bottom is open and holds no pressure- the pressure inside a pipelauncher is dependent on weight of pipelauncher and payload with whatever acceleration is wanted (each gee doubles it's weight).
In a sense you can think of a pipelauncher as a 2 dimensional boat- though since boats usually have a bottom, this "boat" is upside down:)