Claire Manton has become Brighton club's first English Schools champion for 15 years.
The 13-year-old Sussex and Southern Area champion took the 100m junior backstroke crown in a personal best 1min.06.74sec at the Isle of Man meet.
Imberhorne (East Grinstead) pupil Ben Hutchinson, 13, from Crawley club, made it a county individual double when he secured the 100m freestyle crown and their success ensured the pair England debuts in the Home Internationals in Wrexham next March.
Blatchington Mill pupil Claire, from Hove, said: "I am very happy to be the club's first winner for so long. It feels great to be a national champion. It was a tough competitition. I didn't expect to win when I saw the programme and who was competing against me.
"What helped me was the support I had. It was fantastic.
"I am really excited about making the England team too. I would love to swim for my country as a senior one day and, hopefully, in the Olympics."
Claire was part of a combined counties team, also involving Dorset (Leanne Studley and Gemma Smith) and Hampshire (Laura Chase), that claimed the girls' junior freestyle relay crown.
She has worked hard for success, training five nights a week for two hours at St Mary's Hall (Monday), Surrenden pool (Tuesday), Brighton College (Wednesday and Thursday) and Prince Regent (Friday) .
Claire said: "I do it because I enjoy it.
"I don't have a social life outside of swimming, although I used to have a pony called Fizzy that was kept in Pyecombe for me but I outgrew him. Yet I don't mind because I see my friends every night because they are members of the club like me."
She also has had to endure nightmare trips to and from the Isle of Man with her Sussex, Hampshire and Dorset team-mates.
"It took us about 23 hours to get there and it was about 18 back because of the bad weather, train and ferry problems. The waves were very choppy and I felt a little seasick. I didn't get back home until 2.15am in the morning. But it was all worth it."
Brighton, formed in 1860 and rated the oldest club in the country, are delighted.
Press officer Brian Smith said: "Our last champion was Teresa Dray 15 years ago and she was the first. It is has been a long wait for the second. It is quite a feather in our cap to get another."
Hutchinson also combined with twin Chris and Danny Sivers (Eastbourne) to win the junior boys medley winning team.
The twins' mother Rosie Hutchinson said: "Both boys did so well. I am so proud."
Only individual winners qualified for the England team, but Sussex produced two silver and two bronze medal winners.
Second were Hastings Seagull Lisa Chapman (Hastings College), 16, in the girls' senior 100m backstroke and Shiverer Charlie Ticehurst, 15, from Worthing High, in the boys' 200m individual medley.
Trevor Gaunt , 15, from William Parker School, Hastings, was third in the boys' 100m intermediate backstroke, while Sackville school (East Grinstead) pupil Alex Brown, 17, a Crawley club swimmer, filled the same place in the boys' senior 100m butterfly.
Team manager Tim Hartley, Crawley club coach to Hutchinson, said: "Claire and Ben obviously swam well but I think all the Sussex swimmers in my team did well. They all have a long way to go but many could go a long way. The Olympics? Maybe, but let us see how things go first."
Nicolas Hart (Hastings Seagull and William Parker), Lindsay Waller (Hailsham club and Hastings College), Chris Fieldwich (Shiverers and Worthing Sixth Form College) and Craig Steenhoff (Hailsham club and Hailsham Community College) also competed in the Championships.
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