A Street scuba diver who drowned by the Galapagos Islands fought for her life, an expert said at her inquest.

Donna Maria Newton, 40, of Brutasche Terrace, did two amazing things before she was found floating in Ecuadorian waters last October, Dr Robert Cole told Mid Kent and Medway Coroner's Court in Maidstone on Thursday.

Dr Cole, a diver with 55 years of experience, said: "She had air in her life jacket to hold her on the surface to wait for her boat. And she pressed the button on her emergency beacon, which was brilliant. Very few divers do this. She was fighting for her life."

Miss Newton, a project manager for Thales in Wells, was found floating on the water after becoming separated from her dive party on October 6 last year. Her inquest was held in Kent as her family live in the county and her body was repatriated for a funeral at a nearby crematorium.

She had begun projectile vomiting after eating prawns on the 16-passenger Sky Dancer boat a few days before her death and was found face up in the sea after diving by a search boat with vomit around her nose and mouth.

Dr Cole didn't believe it was motion sickness that would have caused her to vomit underwater as the queasiness tended to vanish under the waves and if she had blocked her breather below the surface she could have cleared it by using the current.

Her diving computer showed her final ascent did not follow the same smooth pattern of her 51 other logged dives.

Dr Cole said: "This is unusual for her and suggests something was happening."

But despite her fast ascent, he said she was still within her safety margin.

Dr Cole was critical of the way things had been run on the Ecoventura trip. Dr Cole said: "In her haste to get to the surface, she blew her life jacket and activated her radio and beacon. I find that very upsetting they didn't check to locate her that way.

"The party radioed the mother boat to get the oxygen ready. Why was it not on the panga boats? It might not have made a difference, but it might have given a chance."

Each diver was assigned a dive buddy to keep an eye on each other every time they went underwater. Miss Newton's dive buddy was an American called Pamela Hagendorn, who shared a cabin with her on Sky Dancer.

On October 6 the first dive of the day went without a problem.

But during a second submersion the dive buddy said she was instructed to resurface before running out of air. She didn't notify Miss Newton, 15 feet below her and swimming with turtles. That was the last time the qualified diver was seen alive. When the American broke the surface, she was collected by the group's waiting panga. When the rest of the dive party resurfaced later, Miss Newton's absence was discovered and a search was launched. The second diving group's panga found Miss Newton floating near the first diving spot. Efforts to resuscitate her failed.

Dive master Fabricio Carbo described himself as the most experienced diver on the Galapagos Islands and said it was the first accident that had occurred on his watch in his 27 years of experience. One of the rules of the trip was no solo diving, meaning buddies must stay together at all times.

But a French couple on the boat, known only as Erik and Marie, made contact with Miss Newton's parents and criticised the master's use of mixing-and-matching dive buddies to suit circumstances and claimed he swam on to new sites without checking all his party was in tow.

The coroner Roger Sykes said he would record a narrative verdict – a summary of how Miss Newton came to die – once he had reflected on all the evidence he had heard.

The final verdict is expected at the end of this week.