The popular units at Geordie Bay were built in the wrong place.
They are too close to the water.
And during winter storms, ocean water laps up to their foundations.
According to Rottnest Island Authority chief John Driscoll, they will eventually fall into the ocean. The same applies to units along Thomson Bay.
The authority's 20-year strategy says the effect of rising sea levels is "already evident on Rottnest - with insidious coastal erosion a reality".
As a solution, it proposes to offer the accommodation units at Geordie and the neighbouring Longreach Bay to a private operator, with a view that the front row of units will eventually need to be rebuilt further up the dune.
In exchange, the operator would be offered land between the two bays for an eco beach resort, "sensitively located to take advantage of the dramatic outlook". This resort would offer "upmarket" accommodation.
"The new development will also redefine the visitors' arrival at the tourist area of Geordie Bay, with the potential to offer a contemporary and architecturally designed series of related buildings that maximise the benefits of the site whilst providing a high level of service, accommodation and amenity for the visitor," the plan says.
In Thomson Bay South, similar erosion problems exist.
A highly eroded steep dune face in the front of accommodation threatens the units and they need to be rebuilt.
These will also be offered to a private operator.
With all staff accommodation to be rebuilt on Brand Way, existing staff quarters could be redeveloped by the same operator into more tourist units.
"Thomson Bay South is an area that is likely to see substantial development and change over the next 20 years," the strategy says.
"The existing accommodation stock is some of the oldest on the island and some of the units are located close to an eroding shoreline.
"Rebuilding this accommodation is likely within the next 20 years, however this redevelopment may well be part of a commercial development rather than a RIA venture."
The plan says an important focus is to enable the private sector to "increase and improve the accommodation offerings by providing modest to luxury accommodation through various forms such as building and leasing".
At Bathurst and Thomson Bay North, accommodation units will remain under the management of the RIA. But much of the infrastructure is ageing, the units have limited or no views and the landscape is dominated by sand and mulch.
The plan proposes irrigated lawn in "pocket parks" where families and friends can gather for barbecues and picnics.
It also suggests new composite decks in the backyards of the units to create connections to the rarely used shared spaces at the rear.