Missy Franklin has her sights set on eight events at the world championships in Barcelona as she heads a youthful US team aiming to maintain American dominance despite Michael Phelps' departure.
Spyridon Gianniotis of Greece defended his title in a grueling and combative 10-kilometre open water event on Monday, surging ahead on the final lap to avoid a sprint with Olympic champion Oussama Mellouli of Tunisia to clock 1 hour, 49 minutes, 11.8 seconds in the waters of Barcelona's harbour.
The pool swimming events begin on Sunday.
The Americans' youth movement was already in evidence at the 2012 London Olympics, where Franklin's five medals included four golds and then 15-year-old Katie Ledecky denied home hope Rebecca Adlington to win the 800 metre freestyle.
Franklin, now 18, set herself up for another strong international showing with world-leading times in the 100 metre and 200 metre backstroke events at the US trials in June, where she also put herself among the world freestyle leaders in winning the 100 metre and 200 metre events.
Franklin is also slated to swim the 50 metre backstroke and three relays, and left Indianapolis focused on getting even faster by the time she arrives in Barcelona.
Ledecky, now 16, won the 400 metre, 800 metre and 1500 metre freestyles at the US trials and finished second to Franklin in the 200 metre free.
However, she opted out of the 200 metres to focus on the longer races in Barcelona.
Kevin Cordes, 19, is another youngster aiming to make a splash after winning both the 100 metre and 200 metre breaststroke at trials.
Cordes booked his ticket to his first major international long course meet, and US men's coach Bob Bowman - who shepherded Phelps through his remarkable career - said he was "very excited" by the potential of Cordes. "He's really amazing," Bowman said. "I can't wait to see what he does."
Bowman noted that Australian and French swimmers have posted impressive times already in this world championship season, but he said the US remained "probably the team to beat".
Bowman seemed confident that young talent will fill the void left by Phelps.
"They're not Michael, but they're still great," he said.
National team director Frank Busch was also bullish, predicting that even without Phelps, the US was "going to be very competitive in Barcelona".
"I can't predict how many medals we're going to win, or how many races we're going to win, lose, or be close on … every time you get some new people in you spread experience around that much more.
"For those athletes where this is their first go-around with it, it's going to be awesome," Busch said.
The newcomers will have plenty of proven champions to look to, including Olympic champions Ryan Lochte, Matt Grevers, Nathan Adrian, Tyler Clary and Natalie Coughlin.
Coughlin, a 12-time Olympic medallist, qualified for her sixth world championships with a victory in the 50 metre freestyle at the US trials.
Lochte won the 200 metre free, 200 metre back and 200 metre medley at the US trials and was second in the 100 metre butterfly.
He will swim the 100 metre fly for the first time in a major international meet, an experiment in a year in which he has admittedly slacked off on his fierce training schedule.
Lochte said these worlds were a stepping stone to the 2016 Rio de Janeiro Olympics.
"The lack of training, it shows," he said. "I'm not coming back as hard as I usually do, and I'm going to change that."