This summer one of my favorite sessions to lead was Water Filtration. During water filtration the cabins would break up into groups of three or four. They would then purchase items that were provided such as rocks, sand, screens, coffee filters, and parts of bottles which could be used to catch clean water.
After using their imaginary money to purchase specific items, the group then works towards filtering the dirty water that was given to them at the start of the activity. The results of the activity can vary, sometimes the water turns out really clean, sometimes it looks the same as the start, and sometimes the group runs out of water.
One of the things I try to get all of the groups to notice is the difficulty of filtering the water. Some of the items like screens and coffee filters always cost more than sand and rocks because they filter out things like dirt and other items from the water better and help towards getting cleaner water. It kind of goes along with the idea of how things that are more useful in life cost more than things that are less useful.
The main thing I want the groups to understand is how lucky we are to have the accessibility to clean water. Because water is such a precious resource that not everyone in the world is able to enjoy.