What safety device must be available and accessible in a pool area?

The essential safety device that must be available and accessible in a pool area is a life preserver or Shepard's crook. This device is crucial for ensuring the safety of swimmers, as it aids in rescue efforts during emergencies. The life preserver allows for immediate flotation assistance to individuals in distress, while the Shepard's crook can be used to reach or pull someone who is in trouble without putting the rescuer at risk.

While a first aid kit is important for providing medical assistance after an incident occurs, it does not offer immediate lifesaving support. A fire extinguisher is necessary for fire emergencies but is not relevant in a pool setting. Crowd control barriers may assist in managing the flow of people, but they do not directly contribute to swimmer safety in emergencies. Consequently, the correct answer highlights a device specifically designed for water safety, emphasizing its importance in preventing drowning and facilitating rescues effectively.