But the experience is not always carefree. Large boats in the East and Hudson Rivers produce strong waves, which makes it hard to stay balanced. “It feels like you are skiing across ice for 20 seconds,” Mr. Kenworthy said.
The Coast Guard has trailed him more than once. There was also that time when his battery died near the Statue of Liberty. He had been with a friend on a Jet Ski, but they got separated, and the sun had set. “I’m out in the pitch black, paddling,” he said. “I had to keep calm and analyze the situation. Which way will the current push me? Where are the boats?” His friend found him about an hour later, and took him back to land on his Jet Ski.
Mr. Sheehy faced a similar situation when his battery died in the Harlem River. A fishing boat picked him up.
“The fishermen told me how dangerous the river is,” Mr. Sheehy said. “It’s a famous dumping ground for bodies because they just disappear.”
Brad Conway, commander of the U.S. Coast Guard Station New York, said that his team had not seen many eFoils yet, but that they are basically simple boards was concerning. “Once you are in the water, off your board, your head is the only thing showing above the water, like a coconut,” he said. “You have someone going through on a speedboat or a Jet Ski, they aren’t paying attention, which is very common, you could get run over.” And as for the batteries’ short lives: “If you run out of battery and drift in front of a barge that can’t stop,” he said, “you might go under.”
Although eFoils, like most water toys (even foam noodles), are legal to use in city rivers, they are not currently regulated by state or federal law, Commander Conway said. But that could change. “It depends on how popular they become, where they start operating, and do they impact other vessels,” he explained. “Surfboards, for example, have never been regulated, but stand-up paddle boards have.” Jet Skis were around for over 20 years before they were regulated by the state in 1999, he said. “It’s the natural evolution of technology, and we have to be ready to look at it and manage it as safely as possible.”