Compatibility summary
You will need a travel adapter in Costa Rica; plug types used there differ from Australia. Voltage differs by more than 20% — a voltage converter may be needed for some appliances.
Plug comparison
Australia plug types: I
Costa Rica plug types: A B
There is no common plug type between Australia (I) and Costa Rica (A B). You need a travel adapter.
Voltage comparison
Australia: 230V, 50Hz
Costa Rica: 120V, 60Hz
Voltage converter recommended (Australia 230V vs Costa Rica 120V).