What do I do about this please? I experience extremely short breaths whenever I get into a body of?

There are two things I can think of that may be causing this.

1. Some sort of anxiety or panicking. Like, if you have a fear of water or maybe a previous traumatic experience with water.

2. A reaction to the temperature of the water. I've heard that people can have reactions such a rashes, swelling and itchiness to do with temperature of water.

I think it'd be best to maybe mention it to you doctor. He/she will probably understand the problem better than I do and might be able to give you something to stop the swelling feeling and shortness of breath.

Hope this answer was helpful. Sorry if it wasn't.