The Murray Mouth is a unique place in as much the shoreline can drastically change overnight, dependant on tidal movements and wind. There are two ways of ingress and egress the area, either by driving along the beach from Goolwa Beach in a 4 wheel drive, or by boat, which can be launched from the No. 19 Beacon.
This area is renown for its Mulloway catches. The best months to fish for Mulloway are from November to end of January. It is during this time when Mulloway make their breeding migration into the Coorong. Winter Months can also produce some catches of salmon as well, but weather conditions are not the best and the area is prone to radical changes in shoreline.
During the summer months, wading out and luring beyond the breakers, or fishing within the Coorong can produce results at dusk and thru out the night. Fishing in the channel is recommended only during calm days, and when the tide turns. The rip thru the channel can be extremely strong, as can be seen when your line and weight moves with the rip.
Even though fishing from a boat in these areas can be an advantage due to your mobility, I wouldn't recommend anchoring in the channel. Also, poor visibility during night time when returning to No. 19 Beacon can be a problem due to exposed mud banks and potential groundings.
If driving by 4 wheel drive, and you intend on staying in this area overnight, I suggest you park your 4 wheel drive as close as possible to the Coorong side of the Sand Dunes. I have seen the tide lapping the back tyres of Chinook's "Truck" at high tide. Mind you, several hours later the water had subsided and the sand was dry enough to drive on. This area is notorious for its changing shoreline.