I usually head to the south side, go down through the huts and drive a bit along the beach. The walk from here to the lagoon is pretty short, usually just fish there. Not sure how long the walk to the mouth would be from the south but i’m guessing it would take a while. Usually plenty of fish in the lagoon but most have been on the small side. I don’t have a 4×4 but if you do there are loads of access roads on the south side further up the river.