Have all captives walk the plank
From Create Your Own Story
One by one, the captives are led along the plank and forced to jump into the piranha-infested Rio Amarillo. The river's yellowish water soon turns a deep shade of scarlet, and alligators join the feast. Maria begs for mercy and has to be thrown overboard by two of your men. As far as you can tell, not a single captive makes it to the shore.
Well... that was entertaining, but rather pointless. When your pirates are done cheering and laughing, it's time to get back to work. You can either sail to the high seas and find something else to do, or stay at the Rio Amarillo and wait for an easier target.