"They've been very patient with us while Waterworld has been unavailable, so we want to make sure we put on something special for the reopening."
Chairperson of the community and services committee councillor Paula Southgate says it is fantastic Waterworld is reopening.
"I think people are going to be really delighted at the improvements," she said.
"I'm hoping all of those people that have had to go somewhere else will come back.
"What is really exciting is that we can now host national swim tournaments, which is really important for a city of our size. It was in a real shabby state — it could not stay like that and Hamilton deserved better."
As part of the The Big Splash, customers will be given the chance to see areas usually off-limits to the public, as many of the improvements have been made behind the scenes.
There will also be inflatable attractions for children, and opportunities to try the new Glidefit equipment and paddleboats.
"We're hopeful of some fine weather leading to a big crowd on the day," Ms Lascelles said.
"If that's the case, we need all our customers to show courtesy and patience."
The Big Splash will run from 10am to 2pm, and the complex will remain open until 8pm after the special activities.
Ms Southgate said: "We see Waterworld as the number one aquatic enjoyment centre.
"It should be the number one destination for water play. In the future, we hope we can improve the outdoor water area and also make improvements around the cafe area."
Operational changes have also been made across Hamilton Pools to coincide with the Waterworld reopening.
They include a change to the opening hours for both Waterworld and Gallagher Aquatic Centre, alteration to the fees and charges for entry and implementation of a wristband system for customers.
Ms Lascelles said parents or caregivers also need to keep Hamilton Pools' supervision policy in mind when visiting either of the swimming complexes.
Those with children younger than five years need to be in the pool with the child, and within arm's length.
Children aged six, seven or eight must be actively supervised at all times by the parent or caregiver they're with, and anyone under 14 must be accompanied by an adult.