With graduation approaching this spring, Jessica McSweeney has a sinking feeling. A senior Human Development major at Cornell University, she has completed her required science and writing classes and looks forward to traveling this summer.

But one thing stands between the 21-year-old Ms. McSweeney and her diploma: three lengths in the school's 25-yard swimming pool.

Cornell students must take the plunge in order to graduate, either by passing a swim test or enrolling in a beginner's swim class. Ms. McSweeney, who hasn't been in a pool much since grade school, is less than lukewarm on the tradition.

"I guess it's a noble skill to have," she says, "but I don't intend to be a water-going person."

Cornell's century-old requirement is among the last remaining at colleges. The tests, which generally require students to prove they can paddle a few lengths of the pool, are among the more unusual graduation requirements in academia. But as schools focus more on career skills than on life skills, support for the requirements has been drying up.

The latest to throw in the towel is the University of Chicago, which announced this fall that it would retire its nearly 60-year-old requirement that students swim 100 yards or take a swim class.

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Evan Cudworth, a 2009 Chicago graduate, isn't sorry to see the test go. Now 26 and working in the school's admissions office, he says most students were "pretty embarrassed that they had to get up in front of their classmates and strip down" into swimwear during freshman orientation.

A University of Chicago spokeswoman says the changes to the physical education requirements were intended to give students more choice in how they exercise. Colgate University sank its swim requirement in 2005 with a bit more of a splash, after a faculty committee called it "arbitrary and indefensible."

There is no clear count of how many U.S. colleges still make students demonstrate swimming skills. A 1997 survey by three North Carolina State University professors found that just 5% of four-year universities required swim tests, while at least 25% had them at one time. (In decades past, male students at some single-sex schools could take the tests in the nude, colleges say.)

Jessica McSweeney

Schools note the importance of being able to swim. "Anything that prevents people from dying needlessly is a valuable skill," says Fred DeBruyn, director of aquatics and assistant physical education director at Cornell. Nearly 3,800 people—more than 10 a day—died from unintentional, nonboating drowning in 2010, according to the Centers for Disease Control and Prevention.

Many nonswimmers don't know how to swim because their parents never learned, so college instruction can "break the cycle" of not passing on the knowledge, says Mr. DeBruyn.

Some high schools still incorporate swim tests.

At colleges that remain swim-test stalwarts—including Massachusetts Institute of Technology, Cornell, Columbia University and the University of Notre Dame—advocates hope the practice will remain. But few can say how the requirements came into being.

A tale at several schools is that the requirement came at the behest of a wealthy benefactor. At Harvard University, for instance, the story was that the school had a swimming requirement because a donor, whose son died on the Titanic, stipulated such instruction as part of a gift. The donor's son did die aboard the ship, but the school says on its "Ask a Librarian" website that "there is absolutely no evidence" that the donor's gift was responsible for the swim test. Harvard got rid of its swim test decades ago.

At Columbia, campus lore has it that a university president wanted to ensure students' survival if Manhattan ever sank—but engineering students could build a boat, so they were exempt. The true story: About 20 years ago, engineers successfully petitioned their faculty to scrap the requirement; other students weren't so successful.

Wartime considerations in the 1940s led to swim tests at schools, amid concern young Americans were unfit for battle. According to Navy historians, 6,720 Navy and Marine Corps officers and enlisted men drowned during World War II.

Washington and Lee University spokesman Jeff Hanna says a school president from the 1910s lamented "the idleness and restless shallowness of the average undergraduate," but it is unclear whether swimming specifically was seen as the remedy for youthful malaise. The school's test now asks students to swim 50 yards in one minute, and then spend five minutes treading water.

Bryn Mawr College's historian investigated the rationale behind the swim test there, but came up dry, says Matt Gray, a school spokesman. Nearly a century after the test first appeared, Bryn Mawr students must swim for 10 minutes, float on their backs for a minute and then spend another minute treading water, or take a swim class before graduating.

"Swimming is a life skill," says Nikki Whitlock, Bryn Mawr's aquatics director.

Ken Torrey, associate athletic director at Columbia, sees no reason to throw the swim requirement overboard. "If it's not broken, why fix it?"

Because it's annoying, say some students.

"You go through four years of classes. I don't think three lengths of the pool should decide whether or not you get a diploma," says Corey Minerva, a 2010 Cornell graduate who put off his test until senior year.

Lisa Bacis, another 2010 graduate, agrees. She flunked her swim test during freshman orientation at Cornell. Twice.

"It was my first thing to do at Cornell, and I failed it," says Ms. Bacis, now 24 and a staff assistant at a cell biology lab at Harvard Medical School. She ultimately enrolled in a swim class.

Students with hydrophobia, physical limitations or religious objections can obtain waivers in some cases. Others manage to swim—or rather, not swim—under the radar.

The Rev. Edward A. Malloy, Notre Dame's president emeritus, graduated without fulfilling that school's swim requirement. An athlete, he was exempt during the basketball season, while lab sessions for his chemical engineering major kept him out of the pool the rest of his undergraduate career.

Shortly before graduation, Father Malloy says, "I had thoughts that maybe [my diploma] would be blank." But he floated right on, ultimately receiving two master's degrees from Notre Dame and serving as its president for 18 years. Now 71, he still can't swim.