The Magpies will face Kaiapoi at Rhodes Park on Saturday, while the other semi-final sees Ashburton Celtic host Glenmark-Cheviot, who edged Prebbleton 15-14.
Waihora captain Liam Robinson said the team played some of their best attacking rugby of the season, despite the poor weather conditions.
"It was pretty funny, we all said afterwards, not many errors and the best with ball-in-hand I’ve ever seen us play in those kind of conditions,” he said.
"Under foot was pretty soft and muddy and wet, but once you get going you’re actually alright.”
Waihora and Kaiapoi have not met this season, but Waihora won 29-13 the last time the sides played in 2024.
"We know they’ve got a solid forward pack, but apart from that, I don't really know too much,” Robinson said.
"(But we’re) very confident, we talked about last year, we probably peaked around this time or a couple weeks earlier, now, after that game, you’ve got to be pretty confident considering that result.
"(The) coaches have been epic, Hagen (Schulte, Waihora’s head coach) has been really good, so hopefully everything can click.”
Although Waihora finished top of their pool, they won’t know if they will host the final until after the other semi-final. If Ashburton Celtic win, they will host. If they lose, Waihora gets the home final.
In other matches, Darfield got up over Ohoka 38-31 in the 9th-12th bracket while West Melton beat Saracens 50-44 in the 13th-16th bracket and Lincoln lost 25-22 to Woodend in the 17th-19th bracket.
Darfield will play Rakaia for 9th/10th place, with West Melton facing Southern for 13th/14th. Springston will play Woodend for 17th/18th place.
