What movie first used a liquid man special effect?

I believe it was Terminator 2 - certainly that was the first with a totally realistic effect.

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Restricted to liquid "man", I would agree with T2 (1991) as the answer. However, I believe the liquid "being" effect was pioneered in 1989 in "The Abyss" when a deep-sea intelligence took on the form of a conduit (or large worm if you prefer) using sea water. The effect was remarkable for the time, especially when the life form copied the facial appearance and expressions of the character portrayed by Mary Elizabeth Mastrantonio. Not as remarkable as T2, but a great beginning.

Micron