What's that in my fuel?

Laid up the outfit and was syphoning the fuel, when I noticed a small globule of smokey coloured oily stuff in the bottom of each jug full. It stayed there so easy to leave behind when transferring to another bike so now out of the system. As I normally dump each tank remainder when swapping by bikes, it could have built up over time maybe. Curious. Bikes been running well but probably not enough of the stuff to get as far as the carbs.

It's probably water.