A bubbler is a type of water pipe that is a smaller, portable version of a bong. Bubblers are hand pipes that feature a chamber with a percolator or diffuser. When dry herbs are packed and ignited, the smoke flows down the stem and through the water, where is is filtered and cooled. This offers a much smoother and cooler than than traditional dry hand pipes. Bubblers are not as big or offer as intense filtration as a bong but are much smaller and far more portable.