Combine the water, soy sauce, Worcestershire, onion,
balsamic vinegar, wine vinegar, lemon juice,
mustard, and garlic in a large measuring cup or bowl
with a pouring lip. This is your marinade.
Place the
steak in a large, zipper-lock bag, pour in the
marinade, and seal the bag. Place it in a flat pan
(in case the bag springs a leak), and stick the
whole thing in the fridge for at least several
hours, or overnight if you have the time.
About
15 mm
the bag, and
broil or grill it to your liking.