My feet float?

I have been a swimmer for a long time and when I was younger the breaststroke was one of my favorites. I was able to swim breaststroke very well until recently. My feet are too close to the surface of the water and I cannot for the life of me figure out what exactly I am suddenly doing differently. It is very frustrating as it really did seem to happen overnight and I cannot seem to fix what seems like simple enough of a problem on my own. Anyone else experience this problem? Any thoughts on how it might be corrected? Thanks!