The latest update (version 12.12.4) to the script adds a new feature - mconfig waterwalk on/off.
Default is on, and before this option existed, it was always on as well.
This option affects how the mapper will on the path to somewhere - with this option off, the mapper will try and avoid rooms you have to swim in, because it is slower. It'll go on land routes instead.
So this option is mainly good for newbies or people who can't walk over water - turn the option off to get to places quicker. When you do get the ability to walk on water, turn it on.
By default, its on, because most people can walk over water fine. Enjoy!