You know that Gruntz cannot swim, right? So you also know that Gruntz will not take a path into Water unless there are Stepping Stonez (Bridge Tilez) for them to walk on! So how do you, as a Custom Level designer, deal with Bridgez?
Great big open poolz of Water:
It is useless to create rambling Bridgez of Crumbling Tilez in Water ... the solver only needz to click on a destination, and the Grunt will faithfully take the shortest complete path to that destination! So put Automaticz somewhere in the path, right? Then the Grunt just standz there saying something like "I'm not going there!", if at least one of the Automaticz is down when the solver just clickz on the ultimate destination.
So to ensure that the solver has to actually think a little about how to cross that Water, have at least two Automaticz in the path, with different "Points" valuez ... the delay in millisecondz from the loading of the puzzle before the Tilez will toggle to its alternate state. That will greatly increase the chance that at least one of those Tilez will be under Water when the solver setz out to cross it.
If you have a single path crossing a pool of Water, you might just as well save yourself a lot of time, and make it a straight line, if you don't include Togglerz (Switchable Tilez) or Automaticz!