"It spoils the whole illusion. It's an outrage. I can understand something needed to be done but surely it could've been done better than this."
Fellow Australian Roger Mills added: "The whole experience of visiting the area is very moving but that wall is atrocious."
New Zealand RSA president Lieutenant General (Retired) Don McIver said Anzac Cove was an "extremely important" for Kiwis.
He said it was important that the "iconic geographical site" was kept protected.
Mr McIver said: "A significant number of New Zealanders, of all generations, make the pilgrimage to the site every year.
"The safety of the increasing number of people visiting the area is paramount, but we don't want it to take over from the reverence of our commemorative services held there or the special qualities of the place.
"I assume this sea wall has been designed to safeguard the environment from the sea and provide access by road without the desecration of the whole place."
However, Arts, Culture and Heritage Minister Chris Finlayson supported the decision.
He said: "New Zealand was aware of the construction of the sea wall but is not contributing to it.
"Gallipoli is a fragile environment at constant risk from erosion by the sea and from rain. Unless the work was done, important sites from the Gallipoli campaign would be lost, and so Turkey is to be commended for taking action. It is through their generosity that New Zealanders, Australians and others continue to have access to the peninsula."
The Australian Federal Government backed the work to repair the road above Anzac Cove when it was announced early last year.
Minister for the Centenary of Anzac, Warren Snowdon, said the structure was necessary to protect the numerous famous battlefields that surround Anzac Cove and would be completed well before Anzac Day next year.
Mr Snowdon's office said the Gallipoli Peninsula was being threatened with naturally occurring erosion, with engineers saying the coastline was receding at a rate of 2m every 10 years.
A spokeswoman said: "Without action, the situation will continue to worsen and the area is likely to succumb to further deterioration and ultimately have an adverse effect on the historic battlefields.
"Drainage is a critical element of the roadworks because it ensures the integrity of the road and the stability of surrounding slope - and subsequently the entire beach at Anzac Cove.
"The Australian Government has been assured the work will be undertaken with care and consideration for the natural landscape."