This doesn't explain why they choose to wreck havoc on the 2 poor chickens that are the target of their vengeance.
They have water - not only do they have a decent sized pond to swim in, their is a small overflow stream coming off the pond where they can root for bugs (which they do), there is also a water bucket that is always full which my chickens use when free ranging, AND the ducks frequently stick their head through the chicken yard fence to drink water from the chickens' pen.
They have food - won't use the feeders I put out or eat anything I try to give them on land.
They have shelter - there is a duck house with straw right next to their pond on the bank where they typically sleep. Won't use it or go inside it.