While the top feeders like to say "the cream always comes to the top," in the absence of exceedingly special environments (pure pools of dairy products that in this case may include "bull milk") it's much more appropriate to note that "so does the scum," as that's much more representative of what "the top" consists of in more general situations.

Respected, peer reviewed, and validated reports of research having significantly better credibility than many of the pseudoscientific hallucinations cited here have also found that in a majority of cases most breeding (reproductive) activity takes place near the surface (although the credible reports do also consider some exceptions).

Draw your own conclusions.

In the gene pool, most reproduction comes from .............

John