My mom has that.
She loves to swim too, but really doesnt like getting her head below the water.
Guessing your not a fan of snorkling either?
I'm not afraid to under water, just get freaked out when I find my self in situation where I could potentially drown. I've never snorkled, but I have gone Scuba diving quite a few times, also use to go surfing ever summer when I was living in California.
I had experience where I got stuck under a set of floating stairs in a pool when I was kid and partially drowned. Ever since then I've had a fear of drowning. The only times I've freaked out since I had few times while surfing I tossed pretty badly by waves, disoriented, and got to point where I lost enough oxygen that I pissed myself before getting to the surface. Every time that has happened I'd go weeks without going into the water.