In 2019 the ironically named Tsunami Pool in Longjing, China dished out a heavy beating to hundreds of unsuspecting bathers who, until seconds earlier, had been bobbing about serenely like Cheerios in a breakfast bowl. Fortunately, since we’re living in the smartphone era, this spectacular malfunction was caught on camera, and the resulting footage went viral worldwide.

What had happened here that could result in someone being trashed by an inflatable unicorn? And what’s to stop it from occurring in one of our beloved surf tubs? Let’s find out.

According to Surf Loch’s Tom Lochtefeld, the system appears to be a hydraulic pump-&-dump (you gotta love that terminology), indicated by the large structure from which the wave originates.

Water is pumped into this reservoir at the deep end of the pool; once filled to the desired level, hydraulic gate valves are opened, releasing a surge of water. This surge passes over a contoured pool bottom to form the wave. It’s a wave-generating system that’s been used for many years, including at Florida’s Typhoon Lagoon, Spain’s Siam Park, and the UAE’s Wadi Adventure.

This type of pool has a float-level switch in the reservoir, which cuts the power to the pumps once the desired water level has been reached. A failure of the switch or a power failure between the switch and control room could lead to an overfilling of the reservoir and the ensuing carnage. The other tantalizing possibility is that this was a tactical bomb-set—a final hurrah from a disgruntled employee on their last day of work, maybe? Crank it up to 11, drop the mic, see-ya.

The tsunami at the China pool was the result of a pump-and-dump system. No dedicated surf parks use this type of system.

Wave Pool designers and manufacturers are notoriously cagey when it comes to their tech, but we did manage to glean some insight into how they prevent this type of malfunction from occurring in the modern pools we surf today.

Firstly, the ole’ pump-n-dump is not a system commonly employed anymore. It’s inefficient and offers limited wave variation. It’s also slow to reset as a surge wave creates significant mass transport of water in the pool and increases beach run-up, resulting in longer settling periods between waves. The new pneumatic/hydraulic systems of today oscillate the water already in the pool; no extra water is added, which keeps the time between sets to a minimum.

“We do not generate a tsunami-style wave resulting in significant mass transport and beach run-up,” said Tom. “Rather, our pneumatic wave generators impart a back-and-forth impulse to the water that matches natural wind/wave conditions found in the ocean, resulting in the orbital motion of the water column rather than a tidal wave type of solitary surge.

Tom added that they have numerous circuit breakers, limits on the motor size and amperage cut-off breakers and some other tech safety measures.

Clearly the winner for displacing the most water for the purpose of surfing is Surf Lakes. Contrary to its wild Mad Max aura, the system has several safety protocols in place to prevent mishaps.

A quick look on the internet reveals that of all the surf pools in operation today, it’s Surf Lakes’ giant post-apocalyptic plunger that looks most likely to kill you. But it won’t. Founder and CEO Arron Trevis assures us we can surf securely.

“We have a pneumatic over a hydraulic system that drives a displacement hull,” said Aaron. “Safety barriers around the machine prevent close contact. Control systems manage the forces, and it can only be pushed to a certain height physically. There are a series of safety limits to prevent over-stroking (height the plunger is lifted too) of the machine. Layered redundancy in risk control systems ensures that any over-pressure event trips the machine and it will stop rather than exceed operational limits.”

Aaron added that Surf Lakes monitor the machine and lake operation 24/7 as part of their ongoing service to ensure safe operations and machine optimization and that swimmers are limited to near-shore areas where wave energy has dissipated greatly.

The same goes for Endless Surf who told us that multiple redundancies and physical limitations in their systems are key to ensuring surfers are not caught unawares by a rogue set.

Given the advances in wave pool tech in recent years, we’re unlikely to see failures as dazzling as that of the above again. This may well be the first and last time we see a monstrous inflatable menagerie sweep aside humans in a display of pure hydropower.