This behavior has practically nothing to do with Labradors. Many, many dogs regardless of breed can do this. Cats too. And foxes and wolves and rats and... well pretty much all quadrupeds with reasonable sizes limbs relative to their body. You might notice it's more or less the same motion as walking. Animals that drown usually do so from exhaustion, not because they can't keep their head above water.
Primates are relatively unique in their complete lack of innate swimming abilities.
Primates are relatively unique in their complete lack of innate swimming abilities.