Following a rotors running pick up of Jet A1 at another operators base some years ago my trusty 206L1 settled gently to the ground from the low hover, whilst I was pre-occupied with idly wondering why the TOT was down around 320 C. The engine continued running on the ground.
I, and the ashen-faced refueller, took samples from both aircraft and bowser. Sure enough they were both quote "pristine clear blue, no visible water and a few black pieces of sediment". This is because they were both pure water!
Quite surprising how much a jar of water that's been living in a bowser smells of fuel. Beware.