Two men's sexually inappropriate comments about their female colleague that referenced a hit fantasy television series were not serious enough to justify dismissal, the workplace tribunal has ruled.

The Fair Work Commission held TasWater unfairly sacked two control board operators when it discovered they had joked on the workplace messaging system that one's sexual urges for a young female co-worker meant he might have to join "the unsullied" – a reference to the elite army of castrated warriors on the series Game of Thrones.