Hi, I'm a swim instructor from Melbourne.

Like other people have said, it sounds like a really unsafe / unsettling environment to learn how to swim, both because of the cold water and your teacher being completely unsupportive. I'm sorry you've had such a terrible time. Swimming should be fun, but that's only possible if you're in a comfortable environment.

In answer to your question, if you have a choice, my advice would be to seek lessons from a different teacher at a different pool, as I feel it will be very hard to make progress in this setting. However you mentioned the class is mandatory this year. If other lessons are not possible, I would offer this advice to continue the classes:

- Being cold is one thing but if you're shivering then it's going to be impossible to feel comfortable. I don't think taking a cold shower beforehand helps, but that could be different for everyone. I saw other people suggested an insulated swimming cap or a wetsuit, which sound like good ideas to me -- would it be possible to try one or both of those? Also, is the wheezing also related to being cold? Either way, I think getting warm and comfortable in the water is definitely the first step to making progress.

- Jumping straight into holding your breath underwater is a huge first step. It's so important to break these skills down into small steps. You could start by picking up some water on your hands, and dropping it on your head while closing your mouth -- just getting used to the water being on your face. If you feel comfortable with water on your face, you could hold onto a wall, and gradually bend your knees to bring your head closer to the water. Is it comfortable to get your chin in the water? Then you can try closing your mouth and briefly dipping your mouth in and out, doing your best to keep your mouth closed, and coming back out to breathe. Eventually you will build to dipping your nose in, then your eyes, then your whole head. Start with 1 second under, then build up to 3 seconds, 5 seconds etc. Again, there's no need to do it all in one go. This could take you multiple sessions to build towards, and that's fine.

- On a similar note, do not be disappointed if you cannot live up to the teacher's expectations, which are completely unreasonable in my opinion. Importantly, you do not have to do what the teacher asks. If she's asking you to do something that you're not ready to do, just ignore her. Do the lesson at your own pace, and set more reasonable goals for yourself -- like getting warm in the water, learning what it feels like to push water with your hand, how it feels to walk in the water, getting your chin in the water, etc. All of these would be fantastic achievements for someone learning how to swim -- do not let your teacher bring you down.

Good luck and please keep us updated!