So on this holiday week, what is better than this, the sound of a child splashing. Well, this one just 16 months old, a kind of olympian. But even the strongest swimmers have reason to be cautious... See More
So on this holiday week, what is better than this, the sound of a child splashing. Well, this one just 16 months old, a kind of olympian. But even the strongest swimmers have reason to be cautious because drowning is the leading cause of accidental death for children under five. Tonight linsey davis wants to show us something new. Reporter: Keep an eye on the little boy in blue, watch as he slips under the surface without warning, vanishing immediately. A parent's nightmare, but now picture this, a device that can warn you when your child is in trouble. This is a wahoo swim band. It's worn over the forehead and when submerged longer than 20 seconds, it sends out a signal. These lights start flashing yellow, after 30 seconds it sounds a siren. For kids, it's just like putting on a pair of goggles. How'd it feel swimming having that on? Um, it doesn't really affect how you swim. It's just there. Reporter: For adults, it's a cutting-edge safety upgrade. The new canaan, connecticut ymca paid $30,000 to install the system in this pond, just the sixth installation anywhere in the world. Why did you feel a lifeguard wasn't enough? Because you're only as good as your best lifeguard on a bad day. Reporter: Watch, even in a clear swimming pool, how the movement blurs the presence of a swimmer. In murky water like a pond, it's even more dramatic. Look how this bright yellow dummy just vanishes. For decades, the best way to find a lost swimmer was to form a rescue line, sweeping the area step-by-step. But now, lifeguards can pinpoint a swimmer with this locator. I was a lifeguard, back in 1980 was when I went through my training. Reporter: Hardly anything has changed? Absolutely. Reporter: Safety experts calls this device a game changer. It gives you the ability to learn very quickly that you have someone in trouble, and it gives you the ability to locate them very quickly. Reporter: Technology that not only saves time but could save lives. Linsey davis, abc news, new canaan, connecticut.
This transcript has been automatically generated and may not be 100% accurate.