What is an ordinary foul, and what are common examples?

An ordinary foul is punished by a free throw to the opposing team. Common examples:

• Advancing beyond the goal line at the start of a period before the referee's signal.
• Holding or pushing off from the goal posts, or the sides or ends of the pool, during actual play.
• Taking an active part in play while standing on the pool floor, walking, or jumping from the floor to play the ball or tackle (this does not apply to the goalkeeper within their 6 metre area).
• Taking or holding the entire ball under water when tackled, or deliberately hiding it.
• Striking the ball with a clenched fist (except the goalkeeper within their 6 metre area).
• Touching the ball with two hands at once (except the goalkeeper within their 6 metre area).
• Pushing or pushing off an opponent who is not holding the ball.
• Being in the opponent's goal area except when behind the line of the ball.
• Taking a free throw, goal throw, corner throw or penalty throw other than in the prescribed manner.
• Exceeding the possession time, deliberately giving up possession, simulating being fouled, or going under water to gain positional advantage.

Source: World Aquatics Competition Regulations Part Six, Article 8.