From Manning Base Hospital head south on High St, then down Edinburgh Dr through the dairy farming flats till you get to the Manning River. It seems to be a popular spot any time of day, so you may have to be patient until the locals have walked their dogs or had a picnic right where you want to look. Might as well bring an empty shoping bag to pick up rubbish (CITO) in case you have to fill in time. While there are toilets here, they are not always in the best condition.
Seventy years ago the cache would have been right beside the not so busy Pacific Highway; as it used to cross over from Tinonee by a punt in those days.
This area could be under a metre or two of water in a BIG flood, so it would be interesting to see if the cache survives, as I have not been able to get flood level information about this specific area. [The terrain rating is for those under 6' tall.] (I don't want to make it too easy for muggles).
Why don’t you do a 'Found the Cache' dance, for the GeoMonkeys’ GA0510 cache, http://geocaching.com.au/cache/ga0510, called “Where the h#ll is … ?” Remember, there are many more dance themed caches in the Manning Valley to do your ‘Matt Harding’ http://www.youtube.com/watch?v=bNF_P281Uu4) style dance and get yourself on YouTube!