My word Charmion, I should think the temperature of the water under the ice is probably at or very near freezing. You'd last about a minute then your heart would stop! I've swum in every one of the Great Lakes, in 1967. And visited Ottawa too. (In Canada for Expo '67 in Montreal) but only in the summertime.
My mother and I were both sick in the cinema toilets after watching the start of The Cruel Sea!! My father was thoroughly disgusted with us, but we just couldn't help it. I'm rather pleased (but sympathetic obviously) that I'm not the only one so sensitive to the motion of the sea.
Out of interest, did your father suffer from vertigo? I do quite often, and I have to go to bed for a day or two. I suspect it's all connected with the inner ear and balance mechanisms etc.