The bloody smears left around a person's mouth after performing orals sex on a woman during her period. Named so, due to the bloody residue resembling the scum and water marks left on piers, boats and other structures after the tide has gone down.
Person 1: Oh shit, what happened to your face? You're bleeding!?

Person 2: What? Oh, no... my girlfriend is on her period and-

Person 1: She gave you the Thompson tide marks!? Disgusting! You can get HPV doing that.
by Jim Cognito May 26, 2016
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