When you are told to 'swim good', it usually means that the engagement ahead of you is going to be tough.

Tracing back the genesis of the phrase, you go back to the days of 1700s slavery in the USA, where it was used between slaves to bless another person. 'Swim good' is most likely an ode to the days when slaves were transported on ships, if you were to jump off, you would have to 'swim good' to make it any close to shore.
I: I'm about to jump into the ocean.
II: Swim good brother.
by saveroom October 17, 2013
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