When there is water in front of you or blocking your path, only you can walk through it. If your goblin minions go out of the shallow end of the water they will drown, and can only be saved by blue goblins. Instead of guiding your goblin minions across a complex path to keep out of the water (which they usually fall in anyway and drown), simply walk through the water. Your minions are smart enough not to follow you and will automatically seek the easiest path to get back to you. As long as you leave the Right Analog-stick untouched, they will not enter the water. Be careful; sometimes your minions cannot get through because a bridge needs to be activated (for example, Blue Goblin Cave).