Splash Palace's new $3.2 million hyrdoslides were given the thumbs up by their first riders last night.

Invercargill Mayor Sir Tim Shadbolt will officially open the three new slides to the public on Monday morning. 

But in order to ensure everything's running smoothly for the big day, friends of Splash Palace, Invercargill City Youth Councillors, head students from local high schools and The Southland App were given a sneak peek at a soft opening evening yesterday. 

There are two body slides, measuring 69 metres and 79 metres and coloured green and blue, and a 101m raft slide, coloured red and yellow. It features a large sphere section, which raft riders shoot up into.  

You must be at least 120cm tall to ride the new slides, and lighter than 120kgs. 

That will disappoint small children and large adults, but Stephen Cook, the council's manager of aquatic services, says: "The height and weight restrictions are set by the manufacturers. 

"The weight restriction is 120kg for each of the body slides and 180kg for two riders together on the raft slide. That's set because with the slide, the water and the engineering there has to be a weight restriction. 

"The height restrictions [are because] they are quite aggressive rides - the body slides are moderate and the raft side is extreme - so it's around safety, we don't want young kids using it." 

Cook says age of children is irrelevant, it's just the height and weight. 

For the shorter kids, there'll be changes to the learn-to-swim pool, with a new dolphin inflatable and more toys.  

Aquatics manager Stephen Cook with the slide raft