My experience with women, while statistically insignificant, is remarkably consistent in these two phenomena:
1) She (meaning any woman that I've had sex with) will not accept instruction from me unless I have amply demonstrated my expertise. In this example, when I have her take the tiller, she will be equally or more nervous, if I have not previously proven that I have 100% control of the boat, 100% of the time. Based on the fact that the boat has heeled while I was steering has already convinced her that: a) I don't know how to control the boat 100%, or b) I do know how to control the boat 100% and I am an a-hole for tipping the boat to the point where she got afraid.
2) She will accept instruction from some random bloke that she had not ever even seen before, even if it is the exact same instruction that she rejected when I offered it. Conversely, everybody (including women) thinks that I am a great teacher, except whichever woman I happen to be romantically involved with. It's not just me; I have noticed this phenomenon in all romantic couples who have passed through my corner of the time-space continuum. I have no idea why it's true; I've just learned to accept it.
The moral of the story is: If you want to have fun sailing with a woman, have other people teach her how to sail.