Hi Chris,
Yikes, that sounds a scary experience. Like the others have said flotation aids might work for you, like the water walking belts they have at most Y's. Maybe go with someone at first so they can assist you to get started and feel comfortable so you can do it on your own.
I dont know why I can still swim laps unaided. My legs still feel strong in the water when I do scissor kicking, etc. and I still can manage sit ups so I guess my core is still relatively strong. I feel my weakest part is my pelvic/hip area and thighs. I have lost mass there, but no atrophy, and those joints often ache. Who knows with this weird disorder.
Good luck, Kathy