Then you will want some sort of emulsifying device. These things use rotors with very little space between them, to sort of shear the oil droplets into small sizes that will disperse throughout the water. Likewise, a through run with ultrasound emulsifier may work. But with no emulsifying agent at all, I can't guarantee the emulsion will be stable -- for minutes, or even seconds. Maybe some ionic solid, like NaCl, may provide some charged separation, adding a tiny amount of time to the stability. But you may simply have to work quickly.