Police had to be called to manage traffic delays on the Channel Highway in Tasmania, where cars were lined up waiting to get on to the ferry to Bruny Island.
People took to social media to complain about the lengthy wait on Thursday afternoon.
Some drivers were illegally overtaking across a solid white line to try and escape slow-moving traffic on the highway, police said.
"Police were called to help with traffic control because we were trying to alleviate the possibility of a head-on collision," Acting Inspector Andrew O'Dwyer said.
He said some vehicles had to be moved on to allow traffic through.
"The message is, if you're travelling to the Kettering ferry terminal and get caught in traffic, do your best to keep to the left side of the lane so traffic can still pass."
'Record number' of visitors heading to Bruny
On the Bruny Island Ferry Queue Public Updates Facebook page, travellers described waits of more than an hour to get a spot on the ferry.
Residents trying to get home to Bruny Island said they had never seen the line that long before.
One Facebook user said cars ahead of her were turning around and leaving, while another expressed concern about people having to wait for long periods in their cars in the extreme heat forecast on Friday.
SeaLink Bruny Island issued a statement which said "record numbers of guests are travelling on our services" and called for "patience" during the busy period.
"We have seen an influx of visitors heading to Bruny Island over the Christmas and New Year period and we expect these numbers to continue over the next few weeks," the statement said.
"There are traffic marshals on ground at both the Kettering and Roberts Point terminals to assist with the traffic flow and we kindly ask that you follow their instructions and avoid any queue jumping."
In the past week an estimated 5,800 vehicles and 23,000 visitors travelled on the ferries, SeaLink said.
Long waits for ferries to Bruny Island have been a common story during busy periods including Christmas and Easter.
But that was set to change, with SeaLink taking over the licence in September last year to operate the ferry service and pledging to build two new ferries by the end of 2019.
A third ferry was also added late last year.
