Four American tourists and a local guide were killed when a weekend bachelor party rafting trip in Costa Rica became a "living nightmare."

Three rafts flipped on the Naranjo River at about 3 p.m. local time (1 p.m. ET) on Saturday, and the five victims were carried away downstream, according to the country's Organization of Judicial Investigations.

"What was meant to be a weekend to remember for 14 friends turned into a living nightmare," the survivors wrote in a statement on a GoFundMe page they set up to aid the families of the victims.

The Organization of Judicial Investigations identified the dead as Ernesto Sierra, Jorge Caso, Sergio Lorenzo and Andres Dennis, all of whom lived in Florida and were 25 to 35 years old. The local guide was named as Kevin Thompson Reid.

The group of friends, many of whom had known each other since high school, were celebrating the November wedding of Luis Beltran. His brother, Sergio Lorenzo, was one of the victims, according to Chris Comas, who survived the accident.

In total, there were 14 tourists and five guides aboard the rafts.

Wind and rain initially delayed the start of the rafting trip for less than an hour, the men explained in their statement.

"Within five minutes of being out on the river, all three rafts capsized, and everyone ended up in the water," they wrote. "Everyone struggled to get back on the rafts, with some efforts being successful, but ultimately the rafts continued to capsize due to the immense current. Within minutes, all of us were careening down the river with life jackets and helmets just trying to stabilize and find something to hold on to."

They described a dangerous ride down the river, with all them struggling to stay above water.

The rescue operation on the Naranjo River in Costa Rica. Red Cross of Costa Rica

"Most of us were ultimately able to grab hold of rocks or barriers in or around the water and await the rescue teams to get to us. Unfortunately, not all of us were so lucky," they wrote.

The Red Cross said the rafts overturned near Liverpool de Quepos.

When rescuers arrived, they found three rafts and one kayak overturned, said Luis Guzman, National Deputy spokesman for Costa Rica’s Red Cross.

Guzman said responders were able to rescue 13 people, all unharmed. The five that did not survive were found farther down the river, he added.

After the accident, the survivors got in touch with the American Embassy, which helped the victim's families in the U.S. travel to Costa Rica, Comas said.

The tourists were whitewater rafting in a river that was not a part of the national park. Instead they were in a forest, “an area full of nature,” Guzman said.

Authorities said the river was swollen by rain, and the National Emergency Commission maintained an alert in the area because of the possibility of flooding.

Costa Rican President Carlos Alvarado expressed his dismay about the accident on Twitter.

The Americans arrived in Costa Rica on Thursday and had been renting a house in Playa Hermosa de Jaco, according to the government.