The investor Warren Buffett once gave a famous warning: “It’s only when the tide goes out that you learn who’s been swimming naked.”

The tide has just gone out again, and clues to who’s been swimming naked have begun to emerge.

Mr. Buffett first made that comment in 1992, after Hurricane Andrew exposed the inadequacies of the insurance industry, to describe the rosy appearances that can mask financial recklessness until the good times end.

With a contagious virus seemingly out of control; supply chains disrupted and travel and tourism collapsing; an oil price war that has sent crude prices plunging to their biggest one-day drop since 1991; and stocks that may have just careened into a bear market for the first time in 11 years, the financial system is about to undergo its first real-life stress test since the financial crisis and recession more than a decade ago.

“I’m worried,” the Harvard economics professor Jeremy Stein told me on Monday, as the Dow Jones average was dropping a record-setting 2,000 points. “I don’t usually think of the stock market as having that large a quantitative impact on the real economy. But with credit markets also beginning to show real signs of strain, the potential for damage is elevated.”