It was an 80's film. All I remember about it was this group of
teenagers on a dock in the middle of either a lake or pond. The water
was brownish color. There was a substance floating around in the
water, surrounding the people and killing them. There was one boy
left. He was out swimming the substance and made it to shore. He
started yelling "I beat you, you didnt get me"! the substance
thencovered the boy like a wave and that was the end. I watched this
movie like seventeen years ago. If you know the name, please reply.
Thanks!

Hello.

The movie was "Creepshow 2" (1987).  Specifically, it was a short film
within that movie called "The Raft."

From the Greatest Horror Movie Moments:

"He actually makes it to shore just before the blob reaches him. He
then cackles with glee as he points at the blob, "I BEAT YOU! HAHAHA!
I BEAT YOU!
...The blob then jumps into the air and lands on nerdboy."
http://www.i-mockery.com/halloween/greatest/creepshow2.php

Also see this newsgroup message archived by Google Groups:
http://groups.google.com/group/alt.horror/msg/cc29f3b5e9bbe9e6?hl=en&

"Creepshow 2" DVD at Amazon.com:
http://www.amazon.com/exec/obidos/ASIN/B0000509C4/

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search strategy:
google groups: alt.horror, wave, lake
creepshow "the raft" "i beat you" 

Thanks.

Thank You!!!!

This was based on a Stephen King short story. It was in one of his
anthologies, either in "Night Shift" or "Skeleton Crew"