Thrill-seekers don’t travel to the bottom of the ocean or to the top of a mountain because it’s the safe thing to do. But even by adventure travel standards, the now-missing OceanGate Titan submersible was surrounded by extreme danger.

The experimental vessel took tourists to the crushing depths of the ocean. And while OceanGate CEO Stockton Rush − who is on board the missing vessel − maintained the craft was safe, even “pretty much invulnerable,” he did not seek to hide that the vessel skirted established norms as it catered to wealthy thrill seekers.

“At some point, safety just is pure waste. I mean, if you just want to be safe, don’t get out of bed. Don’t get in your car. Don’t do anything. At some point, you’re going to take some risk, and it really is a risk/reward question. I think I can do this just as safely by breaking the rules,” he told CBS reporter David Pogue last year.

Rush’s own comments — along with lawsuits, expert warnings and a reporter’s concerns — show the vessel took on extreme risks. Now U.S. and Canadian crews are searching for the missing submersible with five people aboard who may have only hours of oxygen left.

Extreme tourism comes with inherent dangers

Step into a row boat at a lake, ride a zip line on vacation or even rent a scooter to tool around town and you’ll sign a waiver making clear you’re taking your life in your hands.

But some extreme – and extremely expensive – once-in-a-lifetime adventures take things to a whole new level.

Every year six people on average die climbing Mt. Everest, this year the number was 13 with four still missing. About 30 astronauts have either died in space or training to get there, and with space tourism becoming a thing, that will likely soon include regular people. At least 180 and possibly as many as 400 wingsuit flyers have died since 1981.