"Tú nadas mucho mejor que él."
Translation:You swim much better than he does.
Habla is the 3rd person form but you would use it with 'you' when you want to be formal. Then you would also be using 'usted' and not 'tú'. So all those 'habla' examples you've seen are just 2nd person formal. The informal 2nd person of 'hablar' would be 'hablas'. Same here: 2nd person - 'nadas', 3rd person (or 2nd person formal) - 'nada'.
That explains why I could not understand the first word, even though I listened over and over, I could not even tell what the sound was. In the slow version, at least it should be understandable, but in this cas I could not tell what the beginning sound was even in the slow version. it sounded garbled.