What must the timekeepers announce or whistle during a match?

The timekeepers must:

• Announce audibly the start of the last minute of the match.
• Signal by whistle (or another audible, distinctive means) when 45 seconds of a timeout have passed.
• Signal by whistle the end of each timeout.
• Signal by whistle the end of each period. This takes immediate effect, except that a penalty throw awarded at the same moment as the end of the period is taken before the period ends. The same applies where a goal is awarded for a ball in flight at the end of the period: the period ends immediately after the penalty throw is taken or the goal is awarded.

Source: World Aquatics Competition Regulations (February 2026), Part Six, Article 3.10.5.