Ryan Gregory was able to swim back for help for his friend, who was still out at sea.
The Coast Guard and beach patrols scoured the water and surrounding beaches until nightfall, then suspended the search.
Coast Guard officials said yesterday that Sterling was presumed dead.
A rising sophomore advertising major at Temple University, Sterling was named the rugby team's rookie of the year as a freshman. He was a key player as a senior on St. Joe's state-champion rugby team the year before.
Last week, Sterling was staying at Gregory's house in Ocean City to play in a rugby tournament Saturday with former high-school teammates, including Gregory's son.
The team played a man down in the tournament to honor him. In a show of sportsmanship, their opponents did the same. His teammates wrapped white medical tape around their wrists with the initials "J.S." and his jersey number.
As videos rolled in the office yesterday, Brian McCloskey, one of Sterling's high-school coaches, recalled Sterling's inviting personality.
"He had the unique ability to make anybody feel like the most important person in the room," McCloskey said.
Ashton Miller, 19, recalled making videos with Sterling, whom he met when they were both seventh-graders touring area high schools.
Miller and Sterling's video "The Real World: St. Joe's Prep," their YouTube spoof of the popular MTV reality show, is another in a long line of digital reminders.
"It's hard to articulate seeing so many text messages and calls" from Sterling, Miller said.
Others on campus remembered Sterling's warm presence.
"He had one of the best smiles I've ever seen," said Tom Farren, head coach of Prep's rugby team. "It was pure joy."
"The only thing bigger than that smile was his heart," said Michael Gomez, principal of St. Joe's, from which Sterling graduated in 2008.
John Sciotto, head men's rugby coach at Temple, said his team would have Sterling's No. 6 jersey on the sidelines of each game next season.
"He was the epitome of a man for others,"said Shaun Kelly, 19, who went to high school with Sterling and was his roommate at Temple.