"what a siren looked like"
Ulysses and the Sirens by Herbert James Draper
Public DomainUlysses and the Sirens by Herbert James Draper

Sirens were creatures of Greek myth, sometimes portrayed as half bird, half woman, sometimes as beautiful women with the tails of fish.  Their song was so enchanting as to be irresistible, and they used it to lure sailors to their death. 

When Odysseus encountered sirens on his long voyage home, he had his men plug their ears with wax to ensure they would not be tempted by the sirens' song.  He had himself tied to the mast so he could experience the song without risk of succumbing.