A South Carolina sheriff’s deputy who died during a dive-team training exercise on Lake Murray last week died from freshwater drowning, according to preliminary autopsy findings released by the Lexington County Coroner’s Office.
Master Deputy Jillian Olson, 29, of the Lexington County Sheriff’s Department, died on July 30 while participating in an underwater training session with the department’s dive team.
The preliminary forensic autopsy was conducted Monday at the Medical University of South Carolina in Charleston. Lexington County Coroner Margaret Fisher subsequently determined that Olson’s cause of death was freshwater drowning.
However, the finding does not explain what caused the drowning.
The circumstances surrounding Olson’s death remain under investigation by the South Carolina Department of Natural Resources (SCDNR), the South Carolina Law Enforcement Division (SLED), and the Lexington County Coroner’s Office.
Deputy was an experienced member of the dive team
Olson joined the Lexington County Sheriff’s Department in 2021 and became a member of its dive team in May 2024.
She was promoted to master deputy in the department’s Warrant Division in March 2025. She had also received the Sheriff’s Tactical Operations Support Award in 2023 and was recognized as the 2025 Outstanding Judicial Services Deputy by the Lexington County Sheriff’s Foundation.
Reports following her death said Olson had recently reached the milestone of completing her 100th dive, underscoring that she was not a novice diver when the fatal training incident occurred.
What happened during the training dive?
The precise sequence of events has not been publicly disclosed.
The Lexington County Sheriff’s Department initially confirmed that Olson died during an underwater training exercise on Lake Murray on July 30 but did not provide details about what went wrong during the dive. Multiple agencies became involved in the investigation.
The subsequent autopsy establishes the medical cause of death as freshwater drowning, but investigators have not announced whether the drowning followed an equipment problem, medical event, loss of consciousness, entanglement, buoyancy problem, or another incident.
At this stage, there is no publicly verified evidence establishing any of those possibilities.
That distinction is important. A finding of drowning describes the cause of death, but does not by itself establish the chain of events that resulted in the diver being unable to return safely to the surface.
A loss felt across the department
Olson was remembered by colleagues, friends and family as a dedicated public servant.
She had moved to South Carolina and joined the sheriff’s department in 2021. During her time with the agency, she took on responsibilities within the Warrant Division and the dive team and was recognized for her service.
Her funeral was held Wednesday in Lexington, where fellow law-enforcement officers, family and friends gathered to remember her.
For the diving community, the incident is also a reminder that experience and training do not eliminate the inherent risks of underwater operations. Dive-team training is conducted specifically to prepare personnel for challenging underwater conditions, but even highly trained divers can encounter emergencies that develop rapidly.
The investigation into exactly what happened to Olson during the July 30 training exercise remains ongoing.
The Scuba News will update this story if investigators release further information about the circumstances of the fatal dive.
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