Everything Under the Moon

You never know when it could come in handy and that first time in deep water is a lot less nerve wracking with an instructor there.

Oh no, you haven't seen me at school on swimming days, I can't, they tried to make me jump from a diving board, I went ballistic, this is panic material, I can't go back there, I'm getting hot all over just thinking about it. I know, it means I could actually drown if I was to fall one day, and I don't want this, but I feel stuck. I simply don't have what it takes.

Then desensitize yourself. Start will soaking your feet if that's all you can stand. You'll be able to stand in a bath tub with only 40 mm of water in it. Just keep increasing the amount so you know it's safe and so you have control of the water. Panic like you describe is often due to a person feeling they have no control of the situation.