Parts of the missing vessel the Margrel, including its wheel and hull, have washed ashore at Goolwa Beach - but the boat's skipper, Tony Higgins, is yet to be found
A boat wheel and part of a cabin were initially located about 11:30am on Friday.
The discovery seems to dash hopes of finding Mr Higgins alive.
Locals Lee Langmead and Charlie Mantell found the remnants before coming across a piece of wood identifying the vessel farther down the beach.
Mr Langmead said debris was strewn along the beach for a number of kilometres between the Goolwa Surf Life Saving Club and the Murray Mouth.
"I reckon it was around four or five kilometres until we found the ships wheel then another kilometre or two until we found the cabin," Mr Langmead said.
"The rest of it [the Margrel] was spread out all the way to the Mouth."
The Times has obtained footage of the discovery which has been provided to SA Police.
More debris is currently being collected and a police spokesperson has since confirmed wreckage believed to be from the Margrel has been located about three kilometres south-east of the Murray Mouth.
Local Police and Water Operations Officers located the bow of the vessel and other debris just before 1pm today. The wreckage along with other items believed to be from the boat have been recovered and will be examined.
This follows a three-day rescue effort to locate the Margrel and its skipper Mr Higgins. The search began on Monday.
Mr Higgins who had been anchored off Granite Island, near Victor Harbor, put out a distress call about 5am on Monday amid rough conditions and was reportedly in knee-deep water aboard his vessel.
The search was called off on Thursday after it failed to locate Mr Higgins or the Margrel.
More to come.