Fake boobs - swimming help or hinderance?

After seeing a very attractive, slim young woman with obviously fake boobs at the pool today, I couldn't help but wonder the impact this would have on your swimming ability...

Do they act as a buoyancy aid? 

Do they weigh you down? 

What's the impact on aerodynamics?

Do they just get in the way?

If said young woman is anything to go by, they are a hinderance, as she spent most of her time standing around posing & pouting while everyone, and I mean everyone, had a good look (me included, obviously or I wouldn't be writing this post) before finally heading back to the sauna after only managing 2 widths. 

However they never seemed to get in the way when Pammy was on Baywatch... 

C.J. always managed to swim out and save lives with no sign of her boobs getting in the way! Or was that just Pammy's excellent acting skills convincing us so???