The footage (at 1:10), taken by a fan in the stands, shows a Bulls fan beside winger Bjorn Basson, who is on the ground.
Mealamu comes over to check on Basson, the fan pats him on the back and as the two players walk away the man throws a water bottle at Mealamu, hitting him on the head.
Soon after Mealamu turns to confront the fan, before Basson and a medical staff member intervene and the fan returns to hit seat.
Blues had the last laugh however, winning the match 29-23, with starter Gareth Anscombe scoring all 29 points.
