However, they returned a short time later, deputies said.
Wells tried to do a flip off the cliff and belly-flopped in the water, deputies said.
"It's quite a ways," said Deputy Bill Malott.
Wells remained motionless for about five seconds and then began to sink beneath the water, Malott said.
Two of his friends dove in the water and tried to rescue him, but they were unable to pull him up, Malott said.
Paramedics estimated Wells was under water for 51 minutes until he was found by a rescue team and pulled out.
Medics began resuscitation measures as soon as they got him onto the boat, said Halfway Volunteer Fire Co. Deputy Chief Doug DeHaven. A Halfway ambulance took him to Washington County Hospital, but by then it was too late.
"You can't explain a tragedy like this, but it seems like there's no rhyme or reason to this," said Tony Muto, whose son played soccer with Wells. "He was a kid who had everything to live for."
Muto, who coached Wells in the past on various youth soccer teams, said his son and the teen were both entering their junior year at North Hagerstown High School.
"Some kids go through school not very noticed. Robby wasn't one of those kids," said Muto, who also attended services at St. Ann's Roman Catholic Church with the Wells family. "He was a very energetic young man and a good student He was looking forward to playing on varsity this year."
Unable to reach their friend when he sank into the water, one of the boys ran to get help. When medics arrived, they immediately began searching the area, DeHaven said.
DeHaven said two boats - one from Williamsport and one from the Washington County special operations team - skimmed the water.
Crew members from one of the boats spotted Wells shortly before 6:20 p.m., but he was too far under the water to reach.
So Halfway volunteer Alan Matheny, an experienced scuba diver, dove in and pulled him up, DeHaven said. He estimated Wells was between 25 and 30 feet under the water.
DeHaven said the water temperature at that depth was in the upper 40s, about 20 degrees cooler than the surface.
DeHaven said divers were already on their way to the quarry when the rescue team spotted Wells. But he said the terrain made it difficult to get him.
"It's a cliff. It's not like Greenbrier Lake or a stream. You can't just walk out into the water," he said.
Malott said teenage swimming in the quarry is a problem that occurs "probably daily."
"We're running them out of here all the time," he said. "There are no-trespassing signs posted all over here and the kids keep tearing them down."
In the parking lot of Hagerstown Block, Wells' friends struggled to keep their emotions in check while they waited for word on his condition.
The boys huddled in a circle and prayed. Some choked back tears.
Realizing that every minute Wells remained under water lessened his chances for survival, rescue workers from five departments searched frantically Tuesday afternoon.
Halfway Volunteer Fire Co. Assistant Chief Jeff Ringer said the quarry's size complicated the search.
"That quarry is deep. It's a deep quarry. God knows where he could be," he said before Wells was located.
Ringer said officials called for a Maryland State Police helicopter, which is equipped with an infrared camera that can search water and detect objects that are warmer than the water.