People are more buoyant in salt water because it has higher molar mass. Humans on average are about 90% density of water by mass so about 10% of your frame would float above the surface, which is generally enough to expose your nose. Of course you can articulate your neck, float on your back, tread water…
Salinity also matters. Salty water you might be up to 3% or 5% more buoyant, pound for pound, compared to fresh water.
Really, it depends on how fat and how salty, but generally the difference is less than 5% by mass.