This is why I provide a concrete number so that people can decide what's cold for them. My experience of temperature is different from most peoples', I'm always cold at what people consider to be normal room temperature, and I'm only warm and happy when the temperature is over 80°F indoors.
I am also not swimming around a lot because I'm doing super macro photography with a diopter, so I'm spending a lot of time in one spot working on getting a focused photograph. However I was also cold during our black water dive tonight when the water temperature was 25° and we were swimming around quite a bit because there was not much to see.
There is a ridiculous biodiversity out here, I saw three species of chromodoris on one of the reefs today! It's also really cool how one dive site is sand with a few bits of coral and then you move over a couple hundred meters and it's a beautiful reef.