I've had zero experience with ponds and have a basic question which I
haven't found addressed anywhere online or in a book. Either I'm looking in
the wrong places, my question is too dumb, or no one who's written about
ponds remembers what it was like to know absolutely nothing about them.

My question is this: If, as I understand it, the pond needs oxygen in the
water to keep from stagnating and to support fish, and if certain plants are
generally used for this purpose, and if one needs a liner in the pond to
keep the water from seeping back into the earth, how are the plants to take
root? Obviously they can't get any nourishment from the pond liner and would
damage it if the roots penetrated it.

I'm having a real problem getting a grasp on this concept. And and all help
will be appreciated, as I am trying to plan my first pond.