Situated in the mountains of Slovenia, the river is one of a number of "unrideable" places that Grubb has targeted as part of the ongoing challenge, with its shallow depth preventing boats from taking to the water.
The promotional clips were also supported by GoPro, who posted it to their official Facebook page. Many of those commenting on the shorter promo clip initially thought the footage was fake and a result of clever editing. Putting any doubters to rest, Red Bull, who the stunt is in conjunction with, laid out the specifications.
In a post titled "What kind of drone is strong enough to tow a man?", Red Bull revealed it took engineers months to perfect. They explain:
It features a battery as powerful as 158 smartphones (1.5 kWh/51.8 V/30 Ah), has rotors with a diameter of 80 cm, weighs 24 kg, and can tow Grubb for up to 10 minutes — even lifting him into the air if necessary. And because it was electric, there was no negative impact on the environment.
Grubb added: "Flying the drone under a bridge feels pretty damn good and tastes even sweeter when you know your good times aren’t causing any harm to the beautiful surroundings.”