King Christian I had 3 000 Danish troops and 2,000 allied Germans. Sture had only about 400 troops in his army, and the Danish could easily pick a fight. In late July 1471, the fleet of 76 Danish Ships with the 5,000 troops set out from Copenhagen harbor to land in southern Sweden.  Sture and Nils Bosson Sture went to central Sweden to gather as much men they could for the defense of Stockholm.  The Danish fleet would have to face the murderous flow of the archipelago that blocked off Stockholm, but managed, possibly with the help of a hired Swedish pilot, to anchor between Käpplingeholm and Wolf's Island  just across the water from Stockholm Castle. Christian decided that a siege would take too long, so he landed in southern Sweden instead. Sten Sture awaited the Danes,  now with 10,000 levied peasants.
Question: What had a murderous flow?
Answer: the archipelago