Clothing can help you float
In most cases, clothing and footwear improves buoyancy during the first moments in the water - because it traps air between the layers when you fall in. Moving less helps the air stay trapped, helping you to float. When put to the test*, most people found floating easier than they anticipated, particularly in thicker winter clothes.
* Based on research conducted by the University of Portsmouth for the RNLI involving 85 participants.