The world's top swimmers will be vying to fill the void left by Michael Phelps as the world championships begin without the decorated American in Barcelona on Sunday.
Phelps, who ended his glittering career after last year's London Olympics, will be watching from the stands at the hilltop Palau Sant Jordi, a venue for the 1992 Olympics, as some of his old rivals bid to take his place as the global face of swimming.
Americans Ryan Lochte and Nathan Adrian, Australia's James Magnussen, Sun Yang of China, Frenchmen Yannick Agnel and Florent Manaudou and South Africa's Chad le Clos will be the ones to watch as the sport comes to terms with the absence of Phelps who amassed 26 world championship and 18 Olympic golds.
Lochte is defending the most titles from the last world championships in Shanghai in 2011, including the 200 metres freestyle, the 200 metres backstroke and the 200 and 400 metres individual medleys.
Among the women gunning for gold medals and world records are Americans Missy Franklin and Katie Ledecky, Lithuania's Ruta Meilutyte, Chinese Ye Shiwen, Cate Campbell and Alicia Coutts of Australia and Ranomi Kromowidjojo of the Netherlands.
Judging by the form book, the Americans are likely to take the absence of Phelps firmly in their stride and top the medals table for 13th time in 15 editions since the first world championships in Belgrade in 1973.
Aquatic super power
The former East Germany briefly knocked them off their perch in 1982 and 1986.
"The United States has been the globe's aquatic power for eons," according to influential website SwimVortex.com.
"Even as the country undergoes a transition period, there is no reason to believe the Red, White and Blue won't remain on top of the world pedestal," they added.
South Africa's Le Clos caused a sensation in London when he pipped Phelps to win gold in the 200m butterfly and deny him a third straight title in his favourite event.
The 21-year-old suffered an injured shoulder around the turn of the year and has decided to compete only in the three butterfly events in Barcelona.
"Michael Phelps was a role model and an inspiration for me when I was growing up so I will miss him a little bit," Le Clos, who has become good friends with his boyhood hero, told a news conference on Wednesday.
"He's going to be in the stands watching and hopefully watching me doing well."
The world championships also offer a chance for traditional powerhouses Australia to redeem themselves after a woeful performance in London.
A damning review said team management had failed to prevent a "toxic culture" from developing in the squad, which produced Australia's worst Olympic results in 20 years.
Abuse of alcohol and prescription drugs, as well as flouting of curfews and bullying, had gone unchecked and contributed to the underperformance, the review said.
The nation's swimmers can put that right in Barcelona and fans will be expecting the likes of Magnussen and Christian Sprenger among the men and Campbell and Coutts on the women's side to step up.
China, meanwhile, are cautiously optimistic and head coach Yao Zhengjie has set a target of four golds.
China finished second behind the US at the Shanghai championships with five golds, two silvers and seven bronze.