Tests have shown that underwater swimming pool alarms perform the most consistently. Underwater sensors alarm more consistently and are less likely to false alarm. When a test object, intended to simulate the weight of a small child, was pushed into a pool, the underwater sensors detected it most reliably. The underwater swimming pool alarms can also be used in conjunction with pool covers, where the surface alarms cannot. Underwater swimming pool alarms are also compatible with pool cleaners if they stay on the bottom or slowly climb the walls. They will not work with some of the new pool cleans that can soar to the surface and swim there and then dive back to the bottom, because this mimics the profile of a small child falling into the swimming pool.
The wristband device also alarmed well but can be impractical because the caregiver must remember to put it on the child, and it alarms when exposed to any water source, even tap water.
Pool alarms should be used as an extra safeguard but should never be relied upon as the only line of defense in preventing a child from drowning in your swimming pool. The keys to preventing these tragedies are by placing barriers around your pool, closely supervising your child and being prepared in case of an emergency.
Resources:
WWW.CPSC.GOV
WWW.POOLCENTER.COM
WWW.SAFETYALARMS.COM