Nothing noticeable. Eight billion people times 100kg average mass, divided by 360 million square kilometers of ocean surface equals 2222kg/square kilometer. Or, assuming the density of a human being 1g/cm^2, a 2.22mm 0.00222mm height difference. Ah, the joys of metrical calculations.

EDIT: Steve pointed out that I was off with my density calculation. Thanks for the hint, coffee was obviously not yet working…