Couch, still only 28, is the most experienced diver in the British team competing in Hungary this week.
She first competed at a World Championships as a 16-year-old back in 2005 when the event was held in Montreal, Canada.
The Plymothian followed that up by competing at Melbourne (2007), Rome (2009), Shanghai (2011), Barcelona (2013) and Kazan (2015).
She has claimed a top nine individual finish at the last four World Championships.
However, in Budapest, Couch will only compete in the synchro event, with Great Britain giving Toulson and Robyn Birch their first individual World Championship experience.
Couch and Toulson have won World Series synchro medals together and finished fifth at last year’s Olympic Games in Rio. But the World Championships in recent years have proved tougher than those events as more teams take part, including many new pairings.
Couch and Toulson will be up against 15 other pairs in the prelims on Sunday morning. They will dive 13th out of the 16 teams.
China’s Qian Ren and Yajie Si will be favourites, but the likes of Canada’s Meaghan Benfeito and Caeli McKay, North Korea’s Rae Mi Kim and Kuk Hyang Kim, Australia’s Melissa Wu and Taneka Kovchenko, Malaysia’s Pandelela Pamg and Jun Hoong Cheong and Russia’s Valeriia Belova and Luliia Timoshinina will all be major threats.
The young German pair of Christina and Elena Wassen will also need watching as will the American, Italian and new Mexician pair.
The top 12 teams in the prelims will progress to the final on Sunday evening.
Meanwhile, fellow Plymothian Tom Daley will open his World Championship campaign on Monday when he competes in the men’s synchro competition with Dan Goodfellow.
The duo won a bronze medal at last year’s Olympic Games, but have had a few niggling injuries this season.
On Tuesday, Goodfellow will team up with his former Plymouth Diving partner Birch in the mixed team event. Former Marjons student Birch will also compete in individual event on the same day.
Daley’s individual competition will start on Friday (July 21). There are a massive 42 entries for the men’s 10m event, so the preliminary round is going to be a long process.
There will then be a semi-final round that same day, with the final scheduled for Saturday (July22).
Daley, who famously won the World Championships as a 15-year-old in 2009, will also compete in the mixed three-metre synchro with Grace Reid on that last day of indoor diving.
The swimming events in Budapest will then take place and will feature Plymouth Leander’s Ben Proud, before the high diving, featuring Plymouth’s Owen Weymouth and Iris Schmidbauer, bring the 2017 World Aquatic Championships to an end.