OXFORD — Annie Krantz dreamed of living in New York City. She painted clouds. She wore mismatched crazy socks with patterns of aliens and sushi. Her favorite author was Kurt Vonnegut and she loved garden gnomes, especially ones with yellow hats.

And swimming, according to her friends, was her favorite activity.

The 18-year-old woman apparently drowned in a Douglas reservoir while swimming Saturday and was identified Sunday by the Worcester County district attorney’s office. Friends said she was a senior at Oxford High School.

“She lost her life because she was so full of life,’’ said Katie-Anne Scott, 18, a close friend who lives in Worcester.

Krantz had attended her senior prom Friday — the night before her death and a week before the Oxford High graduation, said friends.

“Annie was wild,’’ said Sara Stauffer, 18, another close friend of Krantz, who lives in Oxford and attended high school with her. “. . . Her ultimate goal was always to have fun and to laugh.’’

Krantz was swimming in the northwestern section of Whitin Reservoir, a large body of water that partially borders the Douglas State Forest, when she went under the water and did not reappear, authorities said.

A male friend called 911 around 2 p.m. to report that she hadn’t resurfaced, according to a statement by Douglas police Saturday. About 45 minutes after they arrived on scene, divers found the young woman’s body in about 6 feet of water. She was taken to Harrington Hospital’s Hubbard campus in Webster, where she was pronounced dead.

The remote area where the incident occurred is hard to get to — about a mile down a path not accessible to vehicles, said Douglas police Chief Patrick T. Foley.

A sign near a parking area forbids swimming, but no such signs were visible Sunday in the area where Foley and visitors said people frequently swam.

Krantz’ death is under investigation by State Police and Douglas police, according to a statement from Paul Jarvey, a spokesman for the Worcester County district attorney’s office. Foul play is not suspected, Jarvey said in the statement.

Oxford High principal Ross Thibault posted a notice offering counseling hours Sunday morning for students and staff in the wake of “the tragic passing of one of our students.’’

In a statement that did not identify Krantz by name, Thibault told The Boston Globe that counselors would remain on hand throughout the week to help students and staff cope with the loss.

Friends and neighbors recalled the Oxford High senior as an adventurous, “free-spirited’’ young woman who was always smiling.

Though Krantz had been through a lot in her childhood, she “didn’t let it take over,’’ said Stauffer.

Krantz was close with her siblings and loved her sister’s black-and-white cat, Cleo Patrick, so much that he was included in one of her senior photos, said Stauffer. Friends said she had five or six siblings.

“She didn’t care what anybody thought of her,’’ said Dakota Maher, a 19-year-old neighbor. “She’d wear low-top shoes with high socks and a dress. Always happy.’’

Meghan Westerland, 18, a close friend who also went to Oxford High, added, “She could wear pretty much whatever she wanted and get away with it.’’

She was obsessed with the color yellow. She loved Chance the Rapper and Lana Del Ray, glitter and waterfalls. She had a growing collection of almost a dozen garden gnomes, according to her friends. Scott is thinking of getting a garden gnome tattoo in memory of her friend.

“She lived a beautiful and full life,’’ said Westerland, “even though it was horribly short.’’

Globe correspondent Rowan Walrath contributed to this report. Nicole Fleming can be reached at nicole.fleming@globe.com.