They tried fishing in shallow coral flats, stalked bluefin trevally, and even hand-lined over reef—no luck. But just before sundown, they found it: a giant painted crayfish wedged deep under coral.

I’m spending three days deep in the Louisiana bayou on a houseboat with my buddy Murray catching giant alligator gar, chasing crawfish, cooking soul food, and soaking in everything this wild swamp has ...