They say it's best to face our fears. I would spend some time walking and sitting by the water, then sitting with your feet in the water, a slow progression. Do this so that you can feel comfortable with the water. Keep telling yourself how healthy you are and for all you do I'm sure you're in great health! A nice swim would be freeing for you! If you live by the ocean that's even better, sit and relax taking in the sounds, and smell of the water. Sit in the sand and let the water flow over your feet and around you. Become familiar with it, and then venture into it little by little until you feel completely comfortable. Logic tells you that you will be fine, so it's important to face this fear and let it go. I love the ocean and all it has to offer, I'd hate to see you miss out on it. You can do this! Take care.
My advice would be to gradually start exposing yourself to that fear. For instance just swimming a very short distance the first day (then monitoring how you feel) then gradually build it up from there. I think they call it exposure therapy or something.
Please don't avoid swimming altogether as you will feed that fear to such an extent that you will feel anxious anytime you go near the water. Even then, I think yo can still gradually get back into the swing of things, however i think it will be a little tougher.
I'm super scared of heights. To the point where I can't visit one of my friends in his place as he is staying on the 10th floor with an intimidating view from the living room (Glass wall). Funny thing though I don't fear heights when I'm on a plane - needless to say I don't book the window seat.
Hope you get better soon!
Jean-Pierre