Marabou Leech - Leech. The Marabou Leech is considered a must have by the majority of fly fisherman looking for a successful trip. This fly can be used in any form of water, it can be fished in Lakes and rivers, it can even be fished in many salt water locations. Not only is the Black Marabou Leech a diverse fly in regard to location, it is also effective at catching almost anything that swims, this includes, trout, salmon, bass, sunfish, blue gill and the list goes on. Truly this fly does a phenomenal job at doing what is necessary to just simply catch fish.