Candida overgrowth begins in the colon. Over time, as the fungal yeast multiplies it begins to migrate through the digestive tract, moving up into the small intestine, then the stomach (bloating, indigestion), up the esophagus and into the mouth. If it becomes strongly entrenched there you can see a white film on your tongue and inside your cheeks. Once it has moved up to the mouth and you spit into a glass of water the yeast will sink because it is heavier than water. If there is no yeast it will float on top.