A Dartmouth College swimmer died after trying to swim four laps underwater without breathing while on vacation in Florida, authorities said Monday.

The Sarasota County Sheriff's office said Tate Ramsden, 21, was in the area with his family and had gone to the YMCA Selby Aquatic Center to swim laps on Dec. 26.

Dartmouth College swimme Tate Ramsden Dartmouth

Ramsden swam around 4,000 yards — over two and a quarter miles — before attempting an underwater swimming technique called a "100," which is four laps across the pool without coming up for air, according to a sheriff's office incident report released Monday.

During this routine, his sister and cousin noticed a "lack of movement" by Ramsden and he was pulled from the water. He was given CPR and paramedics were called, but attempts to resuscitate him were unsuccessful and the 21-year-old was declared dead at the scene.

The sheriff's office said his death was a "possible drowning" but an autopsy was pending.

Dartmouth College swimmer Tate Ramsden

Dartmouth College President Phil Hanlon said Ramsden — part of the Class of 2017 — was a member of the swim team, the diving team and the Beta Alpha Omega fraternity at the New Hampshire school.

"We have been in touch with Tate's family to share our deepest sympathies with them at this time of heartbreaking loss," he said in a statement. "Our thoughts are with Tate's family and friends at this time of great sadness."