fish in troubled waters - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Try to take advantage of a confused situation. For example, He often buys up stock in companies declaring bankruptcy; fishing in troubled waters generally pays off. This term, first recorded in 1568, expresses the even older notion that fish bite more readily when seas are rough.