James Guy qualified second fastest for the 400m Freestyle final as Great Britain’s swimmers started the Kazan 2015 World Championships in encouraging style.
Jazz Carlin also made it to the 400m Freestyle final while Siobhan-Marie O’Connor and Adam Peaty starred in their 200m Individual Medley and 100m Breaststroke heats respectively.
Commonwealth bronze medallist Guy made his international breakthrough in the 400m Freestyle, finishing fifth on his World Championship debut two years ago.
And the 19-year old has his sights set on improving in Russia, taking his heat out strongly before touching just 0.38 seconds behind China’s fastest qualifier and defending champion Sun Yang.
Nick Grainger finished 14th overall on his World Championship debut, missing out on joining Guy in the final by 0.76 seconds.
Having finished fourth in the 400m Freestyle at the 2013 World Championships, European champion Carlin touched joint second in her heat to book another final berth, qualifying in sixth.
“I think it was just about getting into the meet,” said Carlin. “You’re always a bit nervous but I’m going to go into the final tonight and do the best I can and hopefully I’ll be quite a bit quicker tonight.”
Peaty lowered the Championship record as he shone in the 100m Breaststroke heats on his World Championship debut.
The European and Commonwealth champion – who claimed the world record to win gold at this season’s British Championships in London – will be joined in the semi-finals by Ross Murdoch, who won his heat to progress fourth fastest.
“I was a bit more nervous than usual,” said Peaty. “It was like a final crowd out there and for the heats, that’s a bit crazy.
“But that was the best heat swim of my life so it’s looking good for the semis tonight and the final tomorrow.
“It felt relaxed. I’ve done a lot of work on that front end, keeping it as relaxed as possible. It was a bit tough on the back end but that’s what it’s going to be.”
O’Connor dominated her 200m Individual Medley heat, touching more than 3.5 seconds clear of the field to progress second fastest overall into tonight’s semi-finals.
And the Commonwealth champion, who was eighth in this event two years ago, admitted she had been out to make an impression in her first swim of her third World Championships.
“I think the first swim is an important swim because it sets you up for the week so I’m pleased with that,” said O’Connor.
“I’m looking forward to the semi-finals now – it’s all about putting yourself in a good position for the final.
“You always just focus on your own performance – you can’t do anything about anyone else.”
Hannah Miley also made it through the 200m Individual Medley heats, qualifying seventh fastest for the semis while Commonwealth champion Ben Proud was 11th fastest into the 50m Butterfly semi-finals.
Rachael Kelly came through a swim-off to reach the 100m Butterfly semis after tying for 16th in the heats while Jemma Lowe was 0.26 seconds off a qualification place in 19th.
The men's 4x100m Freestyle Relay quartet were the last Brits competing on the opening morning with Calum Jarvis, Proud, Robbie Renwick and Duncan Scott finishing sixth in their heat and 10th overall, just 0.23 seconds shy of a final berth.