It's been a troubling year for the adventure tourism industry, which offers high-risk travel to customers wealthy enough to afford it, including rocket rides into space, treks to lofty mountain summits, and voyages to the sea floor.

Seventeen people died in 2023 trying to summit Mount Everest in Nepal, and more have needed rescue. Now a massive search is underway in the North Atlantic for a submersible carrying four tourists and a crewmember on a trip to view the wreck of the Titanic.

Critics say this growing sector of the travel industry largely has avoided government oversight, despite a history of accidents and fatalities. For people paying to make trips with a guide or an adventure travel company, it's often buyer beware.

"If you regulate, you're going to kill the sense of adventure, so no regulation was brought," said Alain Grenier, who studies high-risk travel at the University of Quebec in Montreal.

The Titan, the small submersible operated by a Washington state-based company called OceanGate, gives tours primarily in international waters, which means the experimental vessel avoided most U.S. safety rules.

In a 2019 interview with Smithsonian magazine, OceanGate founder and CEO Stockton Rush — currently missing aboard the Titan — complained about government rules.

"There hasn't been an injury in the commercial sub industry in over 35 years. It's obscenely safe, because they have all these regulations," Rush told the magazine. "But it also hasn't innovated or grown — because they have all these regulations."

A for-profit industry with government-funded rescues

Now a massive government response is being led by the U.S. Coast Guard, using vessels, aircraft and remotely operated submersibles, or ROVs.

"There are a lot of pieces of equipment flowing in from St. Johns [in Canada] right now. Some of the ROV capability that's arriving soon is really great," said Coat Guard Capt. Jamie Frederick on Wednesday.

The cost will be born almost entirely by taxpayers. OceanGate required passengers to sign liability waivers, and the company is unlikely to get a bill for this operation.

In a statement posted on Twitter, the company voiced gratitude for "the extensive assistance we have received from several government agencies and deep sea companies."

Vessels from other countries are also involved, as are private ships. NPR asked the Coast Guard for an estimate of the cost of the search and rescue operation but hasn't yet received a response.

Risks and ethical questions for rescuers

Experts say there are also other, hidden costs. The search and rescue operation now underway is happening in a remote area of the North Atlantic, where seas can be rough and visibility limited. That's inherently dangerous.

When commercial adventure trips go wrong, and tourists need emergency aid, first responders often face significant risk.

Dr. Christopher Van Tilburg, an expert in emergency wilderness medicine based in Hood River, Ore., said members of his rescue teams have been injured while searching for lost climbers in the Pacific Northwest.

"It's almost inevitable. I've been on missions where rescuers have been injured. Fortunately, no one catastrophically," he said.

So far there have been no reports of injury among the crews searching for the Titan.

In addition to high profile incidents that involve tour companies, including the vanishing of the Titan, experts say there are also far more travelers taking on high-risk travel alone. Often they lack the experience or the equipment to do it safely.

Scott Van Laer, a former forest ranger in New York state's Adirondack Park, took part in more than 600 backcountry rescues, often involving visitors who were unprepared.

"Most of them are so thankful to receive help, but we have people we had to rescue multiple time for the same lack of preparedness or equipment. So not everybody does get the message," Van Laer said.

Big spenders, big search effort

This massive international response has been mobilized to rescue a handful of wealthy travelers who chose to purchase an extremely risky vacation. Critics say it reveals a stark contrast with the way migrants and refugees are often treated.

"Compare this with the tragedy that happened in Europe with those immigrants who sank, and nobody cared too much," Grenier said.

He referred to an incident last week when a ship sank in the Mediterranean Sea, leaving more than 500 migrants missing. According to Grenier, the search effort and media attention for that disaster were far more modest.

"Now you have the young and famous and the wealthy [aboard the Titan] and I don't think the search effort will stop," he said. "The question is, how far do we go to save people's lives?"