Halifax police investigating the death of a 28-year-old scuba diver are awaiting more test results from the medical examiner.

Linda Palmer, of Dartmouth, died Saturday morning while diving near Sambro Island, south of Halifax.

The diving instructor with Torpedo Rays Scuba was out with several divers aboard a charter boat, the Ryan & Erin, when something went wrong.

A coast guard crew heard the distress call while out on the water aboard an inflatable craft, not far from the divers.

Firefighters and paramedics tried to revive Palmer on the jetty. According to one witness, they gave her cardiopulmonary resuscitation for 20 minutes before taking her away in an ambulance.

"We followed the EHS procedures and tried to resuscitate her on site, but we weren't having a lot of success," said Bill Powell, fire chief for Harrietsfield-Sambro.

Palmer was pronounced dead at a Halifax hospital.

It's still unclear why she died. Police said the medical examiner has completed a preliminary investigation but is awaiting additional test results.

Powell said he heard from the coast guard that Palmer wasn't deep under water.

"She was not in the water, down diving," he said. "She was on top of the water."

Palmer studied education at Mount Saint Vincent University. She taught science at Eric Graves Junior High School in Dartmouth from fall 2006 to spring 2007 before moving to Calgary.

Palmer is being remembered fondly by her friends, many of whom have posted a tribute to her on Facebook.

Palmer is not the first diver to die off Sambro. Powell said he responded to another fatality of a recreational diver three years ago.

"I would say it's safe, but unfortunately it happens from time to time," he said.