Well, in the end, I was persuaded to go on the Breaker Bay (Wellington) mid-winter swim today (21 June 2014 NZ time). The water wasn't that cold at all but, oh my goodness, is it hard to get into the water at Breaker Bay. The shore is so rocky and pebbly, and a downward slope, and everyone was slipping and sliding and falling in the water because the rocks were so submerged.
Still, J and I had a good time, with mulled wine and soup afterwards.
As you can see from the below photo, I am a two-towel person. Also, sneakily, two bathing suits - . don't tell anyone.