What do I do when a player is bleeding or injured?

• Bleeding: order the player out of the water immediately, with a substitute entering immediately, and the game continues without interruption. Once the bleeding has stopped, the player can be a substitute in the ordinary course of the game.
• Other accident, injury or illness: you may briefly suspend the game at your discretion, ordering the immediate substitution of the injured player if needed.
• Restart after a stoppage: the team in possession at the time of the stoppage puts the ball into play at the place of stoppage.
• A player may only leave the water or sit or stand on the steps or side of the pool during play for accident, injury or illness, or with a referee's permission. Otherwise it is misconduct (an exclusion foul).

Source: World Aquatics Competition Regulations Part Six, Articles 9.4 and 17.1 to 17.4.