One of the worst triggers for Tyson’s PTSD is cold water over his head.
Cold water is never fun for him, given the hypersensitive nature of the dog bite scar on his shoulder and the dent in his torso, but cold water pouring over his head is especially triggering for the former Lieutenant.
It’s a mix of his most traumatic memories of Sebastian’s attacks during the monsoon in India and memories of being waterboarded, during his time spent captive in Afghanistan and by his former brothers-in-arms once captured after Moran abandoned Tyson to save his own skin.