Rui, our regular swimming coach, is a dark-haired, sun-kissed, Portuguese janota who looks too warm-blooded and Mediterranean to enjoy the chilly, 15 degree waters of Parliament Hill lido on a Wednesday morning.
So I usually get a sympathetic response when, as one of the few people swimming without a wetsuit, I climb out after 40 minutes to defrost in the showers.
But today, Rui wasn't there. Instead we had a tough-looking drill master with a crew cut, barking instructions like an East End Sergeant Major.
"You're cold?!" he said, as I got out early. It was as if it was the oddest, most unlikely thing I could have said.
"I think it's time I got a wetsuit," I replied. "Never use one," he said. "And I swim all year round. Just swim harder."
He smiled, and I realised that underneath the crew cut, he was a softy. And perhaps, secretly, a little bit impressed that among our group of wetsuit-clad, big-shouldered men, I was the only one braving the cold.