Water accumulating behind the seats is a common ND issue. The manual provides the exact location of the four drain tubes (two behind the seats, two behind the doors). The procedure requires removing the trim panel behind the roll bar. Poking a wire without the manual's guidance can disconnect the tube from the grommet, flooding your carpet.
A genuine manual is broken down into major sections. Here is what you can expect to find for chassis codes ND5RC (1.5L) and ND6RC (2.0L): mx5 nd workshop manual