I sailed across Lake Michigan at night one time at about 4 knots. That was sketchy enough and I knew I was in open water.
Not knowing if you will even see what you'll hit until you have broken your neck against it is not my idea of a good time. Especially if you are going 15kn! It is one of those things you might look back on and glorify a little but when you are there I am sure it sucks.