I'm guessing it was a big swell, which often is accompanied by either a strong current swinging either North or South -- in your case, South. I check Willy Weather and don't fish in swells approaching 3M because of currents -- and besides I don't have any luck -- but some of my mates do. Largest sinker I use in strong currents (usually in swells 2m upward) is a number 3 Star. Other than that on 15lb mono line I just use the lightest sinker that can hold. I really only carry and fish with 2 types of sinkers. You actually don't even need the light sinkers at all unless you are specialising in bream and whiting. You'll even get bream with the big sinker, but whiting are a bit more touchy -- even some bream.
I'm guessing you were night fishing for jews. They like a deep hole with some sand-bar structure around as they are an ambush fish, and look for some white water.
Gutters at Stockton run all along the beach, so unless you are on a bar that comes almost up to the shore you'll be in some kind of gutter. Just pick where the waves are breaking about 30 or so metres out with a gutter between the bar and the shore -- and with white water rolling over the gutter, and you'll be laughing.