Section 2: Equipment

Swimwear: at a water temperature of 18.0°C or above, an Athlete must wear one swimsuit in one or two pieces (not a wetsuit) that has been approved under Article 6 of Part One (Article 10.1 of Part Three).; Wetsuit: at a water temperature below 18.0°C, an Athlete must wear a wetsuit, with only one...

Source: Article 6, Article 10.1, Article 10.2, Article 10.3, Article 10.7, Article 7.8, Article 12.3.1, Article 10.8, Article 10, Article 4.4, Article 4.4.2

Send this to your friend — argument over.