Monday, August 20, 2012

The Day The Submarine Theater Flipped Over

This is a story that, as far as I know, has never appeared in print before.  It’s not exactly hot news—the incident happened in 1970—but it exemplifies Henry Petroski’s dictum that engineers often learn more from failure than success.

One of the big tourist attractions of Texas in the 1960s was Aquarena Springs, an early water park at the headwaters of the San Marcos River in San Marcos, Texas, where I now live.  The park boasted what it called the world’s only submarine theater, a steel-and-glass box with rows of seating inside that you entered via a stairway in the rear.  Once the audience was seated, the entire system was lowered on cables and you watched the level of the crystal-clear spring water slowly rise along the glass picture windows.  When the window was pretty much entirely underwater, the show began.

First came Ralph the Swimming Pig, encouraged to jump into the water by an Aquamaid holding a baby bottle of milk.  Then the Aquamaids themselves put on an underwater show:  not just artistic underwater ballets and blowing huge bubble rings, but unique achievements such as drinking from soda bottles and dining at an underwater picnic table.  Hundreds of thousands of people attended the park each year, and up till 1970 the submarine functioned flawlessly.

Then on May 15 and 16 of that year, heavy rains struck San Marcos and areas to the northwest in its watershed.  Six to eight inches of rain in a day or less produced six-foot-high walls of water that tumbled down normally dry streambeds into town.  An apartment building on the banks of the San Marcos River just down from Aquarena Springs was flooded up to its second story, and the entire Aquarena complex next to the springs was many feet underwater.  Thirty alligators kept in a pen in the park escaped, but that’s another story, although the fact that the park used glass-bottom boats to give tours of the spring may have given rise to the phrase “up to your glass in alligators.”

At any rate, while the submarine theater didn’t flood, the abnormally high water level put a severe upward strain on the lift mechanism, which was designed to support its weight by opposing the downward force of gravity.  Once the floodwaters receded and everything dried out enough to resume operations, the park management asked engineers to come and inspect the lift mechanism for damage.  They said everything looked fine, so the next day tourists were admitted and the show was under way again.

The following information is from a documentary interview with a former Aquamaid who was an eyewitness.  When the first batch of tourists climbed into the theater and the lift mechanism started to lower it into the water, it became evident that the strain of the flood had evidently caused some hidden damage.  Beams restraining the theater gave way, and the thing became a free-floating object for the first time in its career.  With the load of tourists on board, its center of gravity was too high, and the whole theater flipped forward ninety degrees, so that the windows in the front now gave the surprised and shaken-up tourists a view of the bottom.  And of course everybody fell out of their seats.

Fortunately, the open hatchway was still above water in the theater’s new configuration.  Ladders and boats were called for, an escape plan was hastily arranged, and all the tourists inside, at least eleven people, were rescued without injury.  According to the eyewitness, the incident never appeared in the news media, no one complained, no lawsuits were filed, and after repairs the submarine theater resumed normal operations.

However, the park management decided this was a good opportunity to build an even larger theater, which they did.  The new structure was intentionally shaped in the form of three straight sections forming a banana-like curve, which would float upright even if cast free from its moorings in another flood.  It was this theater that I had the privilege of observing this fall when, after many delays, Texas State University (which purchased the park in the 1990s after it ceased profitable operation) finally began reconstruction of the Springs as a nature area.  It took one of the largest cranes in the Southwest to lift the thing out of the water, and if anyone is in the market for a used submarine theater, still good for many performances, I’m sure the University would welcome your inquiry.

This story brings to mind several lessons in engineering ethics.  First of all, the people who design a structure aren’t necessarily the best ones to tell whether subtle damage has occurred to it following an unusual circumstance, such as the flood putting upward strain on a system designed to resist downward tension.  Clearly, the engineers who gave the okay to start using the system after the flood missed something, though it might have been pretty hard to detect exactly what the damage was.

Next, we live in a very different culture than the one that prevailed in 1970.  It is hard to imagine such an incident happening without any news reports emerging about it today.  Kids caught in such a situation would be sending live videos with their iPhones to their friends within seconds, although the solid-steel environment of the submarine theater might have made it difficult to get reception.  In any case, the secret would have been out almost as soon as it happened, and the place would have been as full of news photographers and media helicopters as it was in fact during the final lifting of the theater by the giant crane this spring.  Only back then, the Aquarena Springs management would have been faced with damage control, not to the tourists (no one was hurt, fortunately) but to the park’s reputation.

And finally, the better design of the later, larger theater was directly attributable to the memorable near-disaster that the first one was involved in.  Sometimes, despite every effort designers make to anticipate things that could go wrong, they just miss some tricks that Nature manages to come up with.  So there really is no substitute for experience and experimental trials in some fields.

Aquarena Springs, the theme park, is history now, but it’s nice to know that its biggest engineering failure led not to death or destruction, but simply some good stories a few tourists got to tell when they got back home, and an improved design for the final decade or two of the park’s existence.
And by the way, they did catch those alligators, but they had to hire a professional alligator-wrestler from Florida to do it.

Sources:  Bob Phillips, son of a long-time manager at Aquarena Springs, has produced a 2011 documentary film, “Aquarena Springs and Ralph the Swimming Pig,” available at  I used material on the 1970 San Marcos flood from Jonathan Burnett, Flash Floods in Texas (College Station:  Texas A&M University Press, 2008).   My wife and I took our honeymoon at Aquarena Springs in 1978, surviving a successful submarine theater performance.

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