What are the rules on swimwear, jewellery, fingernails and grease?

Under World Aquatics rules (Part Six, Article 21.5), players must:

• Wear swimwear that meets the World Aquatics swimwear rules.
• Remove anything that could injure or obstruct another player, themselves or an official (for example jewellery).
• Keep fingernails properly cut to reduce the risk of injury.
• Have no grease, oil or similar substance on the body or hands. If the Referee finds it before play starts, it must be removed straight away. If it's found after play has started, the player is excluded for the rest of the match, with immediate substitution.

The SSA U16 National Championship rules repeat these safety points: remove any article that could cause injury, and keep fingernails short.