Peel Regional Police say four suspects were involved in the Aug. 18 robbery, which occurred at the close of an all-night event at the Toronto-area water park.
Police say the suspects forced a group of employees to sit down during the robbery and bound their hands behind their backs.
The park was closed for hours after the robbery as police investigated what happened.
On Friday, police announced they had made arrests in the case and executed search warrants in Toronto, as well as in Mississauga, Ont., and Dundas, Ont.
But police say they are still looking for a Toronto suspect, tweeting on Sunday that 25-year-old David Clarke was still being sought.
Police urge anyone with knowledge of Clarke's whereabouts to contact them. A warrant has been issued for his arrest.