Because my stools have always floated (6years to 67years old), I have either always had the same problem, or floating might be normal for some humans. The only time that my stools have sunk was after taking some antibiotics for a kidney stone problem. About four months after the medication, the floating returned
Stool floats when there's excessive fat in it. You can have a "stool fat test". Reason for fats in stool is fat malabsorption, which may be due to blockage