Travelers arriving from Australia with a valid ETA will be given a Sri Lanka visa on arrival instantly, with no need to complete any paperwork. This will allow them to enter the country quickly and smoothly.
As well as the ETA, they must show proof of funds to support themselves (such as a bank statement) and a ticket for their return or onward journey.
Once this is done, they will be issued with a visa on arrival for Sri Lanka and will be able to clear immigration. This is considered the quickest and easiest way for Australian citizens to visit Sri Lanka.
Australian visitors may apply for a visa on arrival when they reach Sri Lanka. This involves first waiting in a separate queue to apply and filling in the necessary paperwork. This often means wasting a lot of time at border control before being allowed to enter the country.
This option is only available at Bandaranaike International Airport in Colombo.
This is why getting the Electronic Travel Authorization for Sri Lanka in advance is the preferred and most convenient option for Australian nationals.