Depends on the tide, the moonphase, amount of ink fish in the river, etc...
If you sit long enough with a mud prawn a grunter will pick you up anywhere in the river at any time, the take will just differ...
In deeper water (waist and deeper) the take will tend more towards a solid run. Loose drag is the key, count to 5 and tighten up the drag slowly until the resistense is right for the fight. There is also a chance you'll get picked up by a kob and/or a ray here...
Knee to waist water close to prawn banks is where I get most grunter. Make a long cast so they don't see you from the bait. Two tugs and a run, count to 5 and tighten drag slowly.
Shallower water is harder as they are more skittish here. Klein hardegat bytjies, dan kry jy jou hoek mooi blik terug, somtyds met net 'n klein stukkie van die prawn naby the punt van die hoek, hulle steel aas met surgical precision as hulle die dag skelm byt!