Are both lane lines in the lane?

It varies in competition. In many pools lane lines will have around six feet between lane lines, while in bigger pools used for higher levels of competition the distance can be 8 feet or more. FINA...

Section 21460 Double Lines The purpose of the solid-white single line on the inside of the double yellow lines on buffered HOV lanes is to permit vehicles to legally drive to the left of the double...

Well, the lanes are for people who want to do lengths (lengths of the pool). :)

That depends on which country you a driving in.

on a 3 lane road, it is the middle lane.