Rotorua kayaker River Mutton has bounced back from a decent dose of nerves to lead another successful New Zealand assault on the ICF under-23 and junior canoe slalom world championships in Italy.

The 16-year-old had a tough first run in the under-18 K1 division, missing two gates entirely and lying 47th in the 50-boat field. Teammates Lotte Rayner (Central Otago) and Casey Hales (Hawke's Bay) were 27th and 44th respectively.

But Mutton turned things around dramatically in the repechage run, clocking 116.31secs on the tricky Ivrea course to qualify seventh-fastest for today's semifinals.

'I don't think I've ever been as nervous for a race as I was for the first run and it was a pretty hectic but I chilled out way more for my second run,” Mutton said. 'The second run had some alright bits, though I lost a few seconds before the drop, got a little stuck in a hole and picked up some touches but the rest of it wasn't bad and it was definitely a big improvement on my first effort.”

While Hales (19th) and Rayner (23rd) finished out of the running in their second runs, the semifinal onslaught was just getting started for the Kiwis.

Another 16-year-old Hannah Thomas needed only one run to make it through to the under-18 C1 semifinals, comfortably qualifying 12th-fastest, despite picking up a 2sec penalty, with a 115.32sec time.

'There was an awesome atmosphere from Team NZ on the riverbank and that was a big help,” Thomas said. 'The top part of my run was awesome - I was feeling confident and strong on the water but I did have to go back around on Gate 15, which cost me a lot of time, then came low into Gate 17. Apart from that, I put down a solid run.”

Rayner, who had a busy day, was 34th in her first run and 19th in her second run.

Zack Mutton then picked up where his younger sister River had left off, posting the 12th-fastest time in the under-18 men's K1. His 85.23sec time was just 3.80secs behind leading Frenchman Anatole Delassus and nearly 6secs inside the top-30 who automatically progressed.

His 15-year-old teammate George Snook, the youngest member of the New Zealand contingent, posted a 98.29sec time to be 51st after the first run, while Damian Torwick had a nightmare first run to lie 61st.

Tauranga's Torwick, 17, turned things around completely in the repechage run, however. He blazed down the course clean, posting the fastest time of the second run to storm into the semifinals. His 84.96sec time would've been good enough for a top-10 finish in the first run.

The under-18 men's C1 paddlers couldn't repeat the semifinal success, although Tauranga's Stewart Bloor came closest. He posted a clean 102.99sec first run but got stuck in a move just above the finish line, which cost him valuable time and left him in 30th. Jack Egan was two spots further back, after a 104.01sec effort, while Charlie Bell was 44th another 3secs back.

Bloor picked up a touch in his second run to finish 12th, just two spots outside the semifinal qualifiers, with Egan 16th and Bell knocking 14secs off his first-run time to finish 17th.