Can we swim in Gold Coast ( Australia) in July?

Yes, of course you can swim in Surfers Paradise beach in Gold Coast. However, there are 2 main problem.
1. The weather is too cold. I was there in July 2005 (long time ago). Although it's also warm, around 15 - 18 degree, it's too cold for swimming. When you go back to the shore, you will feel the cold wind, not breeze...
2. The wave of Surfers Paradise is to big. It's good for surfing, but not good for swimming.
For me, Brisbane is a boring city. So I will recommend you to go to the suberb area of Brisbane. You can find fruit farm, nuts factories, ginger factory in Yandini (North Brisbane) and also a small rain forest area in Noosa (I hope I remember the name correctly)