Barcelona - Teenage pool star Missy Franklin of the USA will tackle eight events when swimming's world championships start on Sunday as the sport adjusts to life after Michael Phelps.
Having quit after London 2012, after collecting a record 18th Olympic gold medal, Phelps, 28, will only be a spectator during the eight days of swimming's world championships at Barcelona's Palau Sant Jordi stadium.
In his absence, the 18-year-old Franklin will be looking to emulate Phelps, who won eight golds at the Beijing 2008 Olympics, as she looks to tackle a punishing programme.
Franklin's schedule includes the 100m and 200m freestyle, all three backstroke events over 50m, 100m and 200m and all three relays - eight events in total.
Should she win all her events, she will manage something even Phelps failed to pull off. No swimmer - male or female - has ever won eight golds at a world championships.
Having won four golds at the 2012 London Olympic Games and three at the 2011 world championships in Shanghai, Franklin has been working on her 100m and 200m freestyle, where she finished fifth and fourth respectively in London.
The University of California student spearheads a youthful US team which will again be looking to top the medal table.
Other candidates to shine in Barcelona include Franklin's compatriot Ryan Lochte, 28, who left London with two golds, two silvers and a bronze, and has 12 world gold medals in his collection dating back to 2005.
South Africa's Olympic champions, 100m breaststroke star Cameron van der Burgh and 200m butterfly gold medalist Chad le Clos, will be looking to bring more swim success to the Rainbow Nation.
Australia's James "The Missile" Magnussen will be defending his 100m freestyle world title with his team seeking redemption after under-achieving in London and an ensuing tumultuous 12 months.
Their 2012 campaign was Australian swimming's first Games without an individual gold medal since Montreal in 1976 and their worst overhaul haul - of one gold medal, six silver and three bronze - since 1992 in Barcelona.
Two independent enquiries into what went wrong in London pointed to a squad lacking leadership and found "toxic" incidents such as drunkenness and bullying had gone unchecked.
As a consequence, Australia will send their smallest team in eight years to the Barcelona world championships.
Magnussen is targeting both the 50m and 100m events in Barcelona, while five-time London Olympic medalist Alicia Coutts, who like Franklin faces a busy schedule having qualified for five individual events plus the prospect of swimming in three relay teams.
Like the Australians, China's swim team, led by teen phenom Ye Shiwen and distance specialist Sun Yang, will bid to chip away at the United States' pool supremacy.
Sun, 21, led his country to their best Olympic performance in London, snaring two gold medals and smashing his own 1 500m world record as China finished with five titles.
Ye, who is still only 17, will also be in the spotlight as she tries to defend her 200m individual medley world title and again cast off the speculation that accompanied her gold medals in London.
Ye raised eyebrows when she obliterated the 400m medley world record with a sensational freestyle lap, timing faster over the final leg than men's winner Ryan Lochte a few races earlier.
South Korea head to Barcelona without their most high-profile performer and only reigning world champion, 400m freestyle specialist Park Tae-Hwan.
The 23-year-old sits out Barcelona having lost his key sponsor and fallen out with Korean officials, who refused to give him his prize money for his two silver medals in London.
There is plenty of European interest with France's Olympic champion Yannick Agnel, now under the tutorage of Phelps's ex-coach Bob Bowman, racing in the 200m freestyle, which he won last year in London by a body length.
Germany's 200m and 400m freestyle world record holder Paul Biedermann will miss the entire world championships after recovering from illness.
His girlfriend Britta Steffen, the 50m and 100m freestyle world record holder, will not race over 50m in Barcelona having missed the German trials in April with illness, but will compete over 100m.