Is it normal that i can't keep my feet on the floor when. . ?

I have a really bad irrational fear of sharks.
I'm not certain why but this fear has just always been there, ever since I was a child. It has prevented me from going in the sea, swimming pools, and even having baths (don't worry I shower haha). Any body of water makes me instantly uneasy.

When I see one in a film, or a game, or even on an advert, I have a very strange way of coping with it.

I pull my feet up from the floor and sit on the sofa cross-legged and stiff, and cover my eyes. I do this because (as stupid as it sounds) I see the floor as the ocean, and the sofa as my boat, and if I am not touching the water the sharks cannot hurt me or get to me. When I see one it is my first reaction, after the pang of fear through my body.

Is it a normal reaction / thing to do?