A powerful south swell rolled into Southern California on Tuesday, bringing some of the biggest summer surf the region has seen in years and prompting urgent warnings from lifeguards and weather officials.

Summer brings with it the sight of surfers moving seamlessly across wave crests, with ocean waters carrying them along coastlines. A team of scientists has now created a similar phenomenon—with small objects rather than surfers—that can be controlled by humans rather than by nature.

The surf is flat, ocean water is cold, maybe the wind is mucking up conditions — would you travel a few miles inland and pay for machine-made waves? Developers proposing a surf park in Newport Beach have a vision for a place where newcomers can learn to ...