Dig a hole, line it, fill it with fresh water, and you have a water hole: a good place to study colonization. In this outdoor activity, learners create a controlled experiment to study the effects of fertilizer on colonization. Learners create two water holes, one of which uses fertilizer as a variable. Through regular visits to the water holes over the course of eight to ten weeks, learners observe and compare changes. In the process, learner gain a better understanding of the scientific method.