My body doesn't need to survive. It wants to survive. It wants to survive very much. It's the most basic thing it wants to do above everything else[1].
And my body's survival depends on certain things, food, air, certain environmental conditions such as temperature and so on. So, my body wants food, it wants air and it wants to be in a warm and cozy place, out of harms way.
This does not stop me from getting on my bike and cycling to university, despite a bad storm outside, when it is my will to go to university.
I cannot exist seperatly from my body, or rather, my body is an integral part of "me". And my body has rather compelling ways to make its will known to my mind (as you noted with the drowning example). I'll call these urges wants though, not needs.
One good example of how I see this working is, that you can't kill yourself by stopping to breath.
If it was somebody's will to kill themselves, and they therefore stopped breathing, their body will notice how its will (that to survive) isn't being fulfilled. It will then impose this will upon the mind to make it the minds will to breath. If the person uses their willpower not do so, the body takes over, the person passes out and they start breathing again.
(As a sidenote, there might be people that have trained their mind power so well that they could kill themselves like that. Also there are people that have an illness where they can actually die, because they stopped breathing in their sleep.)
Seen that way, I actually have no choice but to do my will. If I saw my body as merely a vessel that I inhabit, then I might sometimes be doing more my body's will than my own.
(And if I had attained Buddhist enlightenment, I'd realize that there's no "I" at all).
Need however, doesn't enter into it.
[1]And that's because species that do not include this will, didn't make it very far in evolution. Even hive creatures like ants have a will to survive. They'll however readily put the will of the entire hive above their own and sacrifice themselves...
-><-
Cardinal Tars Tarkas, KSC. |