When you’re swimming at a public pool, it's always safer to have a lifeguard on duty. But even with that added security, a lifeguard's view of what's going on beneath the surface could be impaired at your local pool.

The height of the lifeguard stand is essential for optimum water safety and to get the best vantage point for surveillance.

Maria Bella, an aquatics and drowning expert, works with swimming pool managers to best position lifeguards and identify potential safety risks. Using underwater targets and three synchronized cameras mounted to represent lifeguard stands at different heights; she compares the lifeguard’s view from each location.

She then presents that information to the pool, and helps them to determine what height lifeguard chairs should be at and where those chairs need to be placed.

“This helps put their lifeguards in a position where they can best identify a struggling swimmer, whether they’re at the surface, just below it or at the bottom of the pool,” said Bella.

In a photo example from a lifeguard position of 2.5 feet, it’s difficult to see two children swimming just below the surface. But if the lifeguard chair is raised to six to eight feet, they become much clearer.

"The higher up you go, the larger amount of the space inside the pool that is easily visible to the lifeguard sitting or standing at a higher perch," explained James Dickerson, Consumer Reports chief science officer.

Dickerson says this phenomenon is due to glare off the water and the refraction of light, when light bends as it travels from the water into the air.

From a low position at the edge of a pool, light refraction from the water and glare from the sun or overhead lighting can significantly limit the lifeguard’s ability to see all areas within the water.

"Glare does present a challenge for our staff on occasion," said Sean Healey, Vancouver Park Board aquatics supervisor, “But our lifeguards have the choice between a sitting position in the lifeguard chairs or a walking patrol and it’s at their discretion given the conditions.”

Healey says the more swimmers create waves which can also change the way the light reflects which is why lifeguards move around.

If you have concerns, ask management at your local pool. And remember, even when there are lifeguards on duty, a responsible adult should always monitor children. Also consider asking the pool management if they’ve ever done an assessment of the location of the lifeguard stands around the pool.

The Canadian Red Cross has a lot of pool safety information on its website. It's not a bad idea to give yourself a quick refresher.