The search for a triathlete who went missing off the California coast after reports of a shark sighting was suspended on Monday, Dec. 22, authorities said.

Erica Fox, 55, went missing off Lovers Point in Pacific Grove, Monterey County, Calif., around noon on Sunday, Dec. 21. The experienced ocean swimmer, who co-created the ocean swim group the Kelp Krawlers over 20 years ago, was swimming with a group of 15 swimmers.

She was swimming back to the point on Lovers Point beach. Her father, James Fox, told NBC News that she and her friends were swimming to a buoy in Monterey Bay.

Around the same time Erica was in the water, two witnesses on shore reported a shark sighting in the same area.

A witness told police that they saw water splashing when the woman disappeared around 100 yards off Lovers Point, CBS San Francisco reports. One person reported seeing a “large splash,” per SFGATE.

Pacific Grove Police Department Commander Brian Anderson told CBS San Francisco that they had alerted all the swimmers to return to shore, adding, “There was one swimmer who hasn’t reported back yet.”

When the group of swimmers returned to shore, they realized Erica was missing.

Summer Day in the Lovers Point, Pacific Grove, Calif.welcomia/Getty

U.S. Coast Guard Petty Officer Christopher Sappey told SFGate that the witness of the shark sighting “claimed they saw a shark breach the water with what appeared to be a human body in its mouth.”

“They then witnessed the shark submerge below the waterline without resurfacing.” Sappey added. “We cannot necessarily correlate this sighting with the missing person as there is no confirming evidence of that.”

Around 7 p.m. local time on Monday, Dec. 22, the Pacific Grove PD confirmed that the coordinated search, which covered over 84 square nautical miles and lasted over 15 hours, was suspended. The search effort included U.S. Coast Guard’s Monterey, San Francisco and Auxiliary stations, the Pacific Grove PD, the Monterey County Sheriff’s Office dive team and the Monterey Fire Department.

“Detectives will continue to investigate the circumstances surrounding the disappearance,” Commander Anderson said in a statement. “We remain committed to determining what happened and following every available lead.”

Pacific Grove, Calif.Getty Images

“The Coast Guard extends its deepest condolences to the family, friends, and loved ones affected by this tragic incident.” Coast Guard Sector San Francisco Captain Jordan Bladueza said.

Monterey Fire Chief Andrew Miller expressed “heartfelt sympathies to Erica’s family and loved ones,” adding, “This is a deeply felt tragedy for our community. We are grateful to all the agencies and first responders who joined the search and provided their support during this incident.”

Lovers Point Beach in Pacific Grove, and McAbee and San Carlos Beaches in Monterey will stay closed through Tuesday, Dec. 23.

Erica’s father told NBC News that he’s in “shock,” adding, “I’m kind of numbed by all this, because it was just out of the blue.”

“Erica was doing something yesterday that she really loved,” James said. “Swimming was her forte. She just loved that.”

“Just an ideal person,” he said. “I’m not saying that just because she’s my daughter, but that’s the way she was — just a wonderful, caring person.”