Carrey, a volunteer marine mammal medic who works full time at Bumblebee Conservation Trust, had just received a distressing text message asking for volunteers to help with 55 stranded pilot whales at a beach in northwestern Scotland.

Immediately, her husband agreed that spending the day pouring water on the stranded whales, making sure their blowholes were clean of water and sand, and doing everything they could to get them ready to refloat was the right way to spend their anniversary, she said.

The couple grabbed a bag of snacks as they rushed to begin the more than two-hour journey from their beach town of Scarista on the Isle of Harris to North Tolsta on the Isle of Lewis.

The island is about a seven-hour drive from Edinburgh.

By the time they arrived, only 12 whales were breathing — eight adults and four calves.

The pod of 55 pilot whales was first reported to the British Divers Marine Life Rescue early on Sunday. Dan Jarvis, the organization’s director of welfare and conservation, said most of the pod died shortly after washing up on the beach.

It is always difficult to refloat surviving stranded whales because of their size and weight, but it was especially difficult in this case because the tide was working against them, Jarvis said.

Still, the group of volunteers, marine charity workers, coast guard officials and others were able to successfully refloat one whale. An investigation is underway to determine how the whales came to be stranded on the isle and their cause of death.

Officials already have a working theory in place. One of the dead whales appeared to have a vaginal prolapse, suggesting that she may have been having difficulty giving birth. Experts think that could be why the entire pod was stranded.

“Pilot whales have strong social and emotional bonds with each other,” Jarvis said. “If one of the whales is in difficulty and becomes stranded, the rest will follow and end up stranded.”

Pilot whales are relatively widespread and notorious for mass stranding, he said.

However, he added that all the evidence must be analyzed before reaching a full conclusion. The Scottish Marine Animal Stranding Scheme is leading the investigation. It is also possible that the pod was sick because of human interference. Only the post-mortem results, which will take a few weeks, can conclude the cause of death.

This could be “largest fatal mass stranding event we’ve had in Scotland for decades,” the Scottish Marine Animal Stranding Scheme said on Twitter. Jarvis said whale strandings are rising in Britain. Experts are investigating why.

Whales can get stranded on the beach for various reasons, including ill health or injury, young mammals getting separated from their mothers or elder ones split from the pod.

Once stranded, the whales can’t make it back to the water and — weighing approximately two tons each — can’t support their own weight, Jarvis said.

Their skeletal structure starts to crush and injuries also start developing from the sand.

Volunteers and whales have to wait for the tide to turn so the mammal can reenter the sea. When the tide shifted, two whales were refloated, but one of them returned to the beach.

Only the other survived, Jarvis said.

It was while waiting for the tide to shift that Carrey, 54, and other volunteers played their part.

She was told that human voices can be comforting to mammals. When she ran out of words for the three whales she was tending to, she began first to hum and then sing to them.

Carrey spent five hours with the whales on the beach, through high winds and rough sea. Just before 4 p.m., it was decided that the remaining whales couldn’t be refloated from the shallow beach and in rough wave conditions, and that they would be euthanized.

“I was singing Scottish Gaelic songs to them,” she said. “And when it was decided that we would stand by, I went to say goodbye to each whale.”

For Carrey, the “intensely emotional day” was “a harrowing experience,” one that she hopes she never has to see again.

“I haven’t slept much since we returned,” Carrey said.

She said the entire island is feeling gloomy. “People are very close to nature here. These whales swim in the waters we see every day,” she said.

This wasn’t the first mass stranding Carrey witnessed near her hometown, but it is the first on which she volunteered to help.

Last year, Carrey took a day-long marine life medic training course on the Isle of Harris, where she learned how to assist in the rescue of marine mammals. Without these basics, taught by the British Divers Marine Life Rescue, she could not have helped the whales in their final hours.

“I have trained for exactly this situation. I had my go-bag ready in the trunk of my car,” she said. “But I never thought I would actually be helping to rescue a pod of 55 pilot whales.”

Carrey’s husband hadn’t gone through training, so he couldn’t be hands-on with the whales, but he played his part by helping to photograph and measure the whales at the end of the day when officials started their investigation.

For Carrey, it’s a wedding anniversary she will never forget, she said.