Familiar places here :) Actually, the word "náplavka" basically means "waterfront" and since there is just one in Prague, there is no need to add the word "Výtoň" to it as "Výtoň" is a name of one particular spot at the waterfront and its proximity (I used to visit the nearby pub "Hostinec na Výtoni" pretty often when I lived in Prague). As for the boats, most of them serve as restaurants and pubs and are permanently anchored to the bank but some of them do cruises as well. Btw I wonder what time you hanged around náplavka to see it this empty. When the weather is nice, the place is usually crowded.

@tipu curate