Daley was the defending champion and he eased into the final with top three placings in both the preliminary round and semi-finals.
But it all went wrong for him in the final, where he finished seventh with just 470.35 points, which was more than 120 points less than he scored to win the world title in 2017.
He did make a great start and topped the standings after round one, claiming a perfect 10 and a score of 93.50 points.
However, in round two he dropped down to fourth with 72.00 points.
Another average dive of 77.40 points in the third round left him down in sixth at the halfway mark, but he was only seven points off a medal placing.
Despite scoring an improved 84.00 points in the fourth round, Daley, who was looking for a third world title, saw his rivals open up a gap and then any hopes of sneaking a medal went with his fifth round effort, which he dropped totally to score just 46.25 points.
To his credit, he did bounce back from that and finished the competition with a stunning three-and-a-half back somersault pike that scored him 97.20 points.
Although he was disappointed to miss out on a medal, by reaching the final he did qualify Great Britain a spot at next year’s Tokyo Olympic Games, where he aims to put things right.
“It’s not the way I wanted to end the World Champs but on a positive, I came here to qualify two Olympic spots and I managed that, and I came away with a medal in the (men’s) synchro,” he said.
“Of course it would have been nice to go out there and win or win a medal, but it leaves me some room for next year, gives me some things to work on and some extra motivation.”
China’s Jian Yang and Hao Yang made a serious statement in Gwangju, finishing with 598.65 points and 585.75 points, respectively, to win gold and silver. Russia’s Aleksandr Bondar was third 541.05. Ukrainian 13-year-old Oleksii Sereda claimed an impressive fourth place with 490.50 points.
Daley, who had picked up a bronze with Matty Lee in the men’s 10m synchro competition earlier in the week, also missed out on adding another medal to his collection in the mixed three-metre synchro competition on Saturday morning.
The pair were nicely poised in third place after rounds two and three thanks to some solid diving.
However, they slipped to fifth in the penultimate round after a mistake, meaning they needed something of the highest order to make the podium.
Producing the best dive of any pair in the competition, Daley and Reid scored 73.47 points for their final round front three-and-a-half somersaults pike to provisionally lie third, but it wasn’t enough as the Australian’s delivered a quality final dive to clinch gold and push the Brits down into fourth.
“This event is always so close because everyone is doing a similar degree of difficulty dives,” said Daley. “I messed up my fourth round dive a little bit, so if I’d have done anything near normal we’d have been up in the medals and maybe contending for gold.”
The action in South Korea moves to the swimming pool on Sunday where Plymouth Leander’s Ben Proud will be looking to defend his 50m butterfly title.
Proud swims in the heats of that event on Sunday but his main focus is like to be on the 50m freestyle later in the week.
Joining Proud in Gwangju is Leander’s Laura Stephens, who will swim in the 200m butterfly event on Wednesday.