David Davies stormed home for a superb victory in the men's 1500m freestyle to claim Wales' first Games swimming gold.
Davies is Wales' first Games pool champion since 1974
In doing so, the 21-year-old, who also won bronze in the 400m freestyle, became his country's first Commonwealth swimming champion in 32 years.
England's Liam Tancock, Christopher Cook, Matthew Bowe and Ross Davenport took silver in the 4x100 medley relay.
Scotland took bronze but Australia won in a new Games record for their only able-bodied men's gold of the event.
Gregor Tait, Todd Cooper, Craig Houston and Kris Gilchrist's third-place finish completed an amazing Games for Scotland.
The 12 medals in the pool make swimming the most successful sport in Scotland's Commonwealth Games history, beating the 10 medals won for judo in Manchester four years ago and for athletics in Brisbane in 1982.
Gilchrist just missed out on a 13th medal in the 200m breastsroke after finishing 0.53seconds behind Australian bronze-medallist Jim Piper.
Davies added the Commonwealth title to the bronze medals he won in the event at the World Championships and the 2004 Olympics.
The result was rarely in doubt - by the time he reached the 1000m mark, South Africa's Hercules Prinsloo was his nearest challenger but almost 10 seconds adrift.
It means Davies became the first non-Australian Commonwealth champion at this distance since the 1954 Vancouver Games.
Canada's Andrew Hurd was second in 15:09.44, with Prinsloo third in 15:11.88.
"All week I've been in a no-win situation as everybody expected me to win," Davies said.
"It's great to finally race and get the pressure off my shoulders. It gets harder. When you are doing it on your own it's really tough.
"It was all about putting in a good performance and getting a place on the podium and not the time."
England's Mark Foster, meanwhile, was just pushed out of the medals in the final of the men's 50 freestyle in Melbourne.
Foster, the 1994 and 1998 champion was always behind after a slow start off the blocks, finishing in 22.49 secs.
South Africa's Roland Schoeman won his third Melbourne gold in a new Games record of 22.30 from Canada's Brent Hayden and Australian Brett Hawke.
Foster said: "It's my last Commonwealth Games so it's disappointing. I had a slow start and it cost me."
Schoeman's other gold medals at the Games came in the 50m butterfly and as a member of South Africa's 4x100m freestyle relay team.
"I'm excited, it's awesome," Schoeman said.
"I knew I needed to have a better start in this final and fortunately I did.
"I touched the wall and saw there wasn't anyone too close to me and I thought 'yeah'".