A roving security robot — oblong and about four-feet-tall — plunged into a water fountain outside a Washington, D.C., office building Monday afternoon, sending online commentators into a tizzy and causing many people to spot plenty of metaphors for the much-promised autonomous future.

Numerous photos posted online showed the robot on its side in the ankle-deep water as workers tried to figure out how to rescue it.

The autonomous machine was apparently making its usual rounds outside the Washington Harbour office and retail complex in Georgetown when it tumbled down some steps and into the fountain. The robot began operating at the complex in recent days, according to an office worker.

Knightscope, a Silicon Valley start-up, said in a statement that the incident was under investigation, pointing out that no one was hurt. The company called it "an isolated event" and promised to deliver a new robot this week for free.

Meanwhile, online observers were having a field day.

The robot's fate was unclear late Monday.