A jump into Barton Springs Pool raises goosebumps and turns lips blue. That’s what 68-degree year-round water does to a body, right?

Not so fast.

Despite T-shirts that proclaim it, websites that tout it and a Wikipedia entry that boasts it, the water temperature at Barton Springs isn’t 68 degrees, and rarely has it been.

Walker Stone, left, drops a multi-sensor probe into the water near the dam at Barton Springs Pool. Photo by Nick Wagner/American-Statesman

We headed to the pool this week with David Johns, a hydrogeologist for the City of Austin, and his assistant, Walker Stone, to dunk a multi-sensor probe into three locations at the spring-fed swimming pool and let science do the talking.

Our results? At the fault line next to the diving well, near the main spring, the temperature read 70.6 degrees. But at the surface by the downstream dam, it was 71.6 degrees. It was even warmer at the shallow end of the pool, where it measured 74.9 degrees.

Myth busted, then? Sort of.

David Johns, left, and Walker Stone, right, check the temperature near a spring at Barton Springs Pool. Photo by Nick Wagner/American-Statesman

The pool has, at times, measured 68 degrees. But it’s not all that common, and certainly not during the summer, when most people are taking that polar bear plunge. The temperature varies slightly, depending on time of year and discharge volume. Mostly, it depends on what season rains fall.

The 68-degree myth has been propagated by the City of Austin website which long stated that the pool water hovered around 68 degrees year-round. Today it reads “average temp of 68 to 70.” Still not quite accurate, but closer than the Wikipedia entry for the pool, which boldly states, “The pool is a popular venue for year-round swimming, as its temperature maintains a stable 68 °F (20 °C) in the winter and summer.” 

RELATED: Have you ever swum naked in Barton Springs Pool?

Want more evidence? The USGS monitors a probe placed in a small opening at the bottom of the pool where spring water comes out, taking temperature measurements every 15 minutes. That’s typically the coolest spot in the pool during the summer, and the temperature there has held a consistent 70.5 degrees there during the last few weeks.

Walker Stone takes a temperature reading (in Celsius) at Barton Springs Pool. Photo by Nick Wagner/American-Statesman

“Some people say it seems colder than that, but it’s still 30 degrees colder than body temperature, so it’s cold,” Johns says.

Still get goosebumps when you leap in? That’s OK. We do too.

“For you and me, it’s still bracing,” Johns says.

Read more about the pool’s temperature in an upcoming story.