So we think that we can actually clean the oceans."
Slat came up with the idea seven years ago, drawing it on a paper napkin when he was still in high school.
It seeks to use ocean currents to gather up some of the bottles, plastic bags, flip-flops and other detritus that sully the planet's waters.
The system has been undergoing tests for the past year.
- 'A big day' -
The Maersk Launcher ship finally sailed from San Francisco on September 9 for trials on cleaning the patch, a floating trash pile twice the size of France that swirls in the ocean halfway between California and Hawaii.
It was towing a 600 metre (2,000-foot)-long boom device designed by Slat dubbed System 001, aimed at containing floating ocean plastic so it can be scooped up and recycled.
The system includes a tapered three-metre skirt to catch plastic floating just below the surface.
Slat said that before the plastic was "still escaping the system" by riding over the top of the boom..
"And that's now what we've been able to resolve by having what you call a corkline, so a sort of a large barrier that's floating on the surface, which prevents plastic from actually leaving the system again," he said.
"I think I have to be happy. Today is a big day."
Eventually, Slat has said he wants to create a far bigger, 100-kilometre (60-mile) long V-shaped barrier made up of large, rubber pillow-shaped buoys.
The youngest ever winner of the Champion of the Earth award -- the UN's highest environmental honour -- Slat gave up his studies in aeronautical engineering to pursue his project...……………..More