UK, Australia, New Zealand, Canada and USA passport holders don’t require a visa for a stay of less than 90 days.
South African passport holders REQUIRE a visa (issued before departure). Requirements for the procurement of a Croatian visa are subject to change but application requirements include the need to show proof of sufficient funds to cover duration of stay, proof of pre-paid accommodation or documentation regarding the purpose and means of travel (such as a return or onward ticket, details of holiday arrangement etc).
Croatia visa information for South Africans: http://www.mvep.hr/
For passport holders of other nationalities not included here, please check the Project Visa website for more information.