Concept: Psychological (olfactory?) warfare with durianwani. When they get territorial they’ll give off a musk that stinks to high heavens, and Crocodile has trained a half-dozen of them to do it on command.
The smell is potent enough to have Navy patrols sailing off course for leagues just to avoid it. Sometimes even into dangerous currents.
Durianwanis have a scent that can politely be described as "a cocktail of spoiled milk, dead skunk, and sweat socks pickled in rotten onions, all coated in a thick layer of raw sewage and left to sit in the sun next to a dumpster of fish for a week straight" The wani handlers can't even get near one without a hazmat suit or they'll puke if they catch a single whiff of wani stank. And all those durianwanis converging on those battleships with a vengeance.
Vice-admiral Hound, nicknamed as such for his unparalleled sense of smell, fainted before navy ships came within sight of Karai Bari.