The Pool Patrol PA-30 Pool Alarm gets the top nod here because of its versatility. It will work equally well in either an in-ground or an above-ground pool. The alarm is equipped with a remote sensor that sounds both the pool alarm and the remote alarm, which can be located up to 200 feet away. It floats on top of the water, which means installation is a snap, and it reacts to any wave that is created when unauthorized pool use is in progress. It is adjustable for sensitivity, which will inhibit false alarms, and runs on one 9-volt battery.
If you are only looking for a pool alarm for your in-ground pool, you can't do better than the Aquaguard Pool Alarm System. It works by sensing water pressure and will sound the alarm at anything entering the pool that weighs over 18 pounds. It features dual alarms in the unit and comes with a wireless remote receiver that has its own alarm which sounds when the main unit goes off. It is one of the best alarms at identifying false signals, like wind or rain, and it will rearm itself after everyone has left the pool for the day. This is the best alarm for in-ground pools.
This is considered one of the top model of pool alarms made. There is no doubt that in static testing it virtually always comes out on top, but the SENSOR ESPIO In-Ground Swimming Pool Alarm Remote in the real world isn't any better than other top choices, and it is also more expensive. That it is a fine pool alarm cannot be disputed, it has one of the loudest alarms of any unit and installs semi-hidden beneath the pool deck. It can even be permanently mounted during pool construction. The unit must be submerged about halfway into the water to be effective, it comes with a wireless remote, is magnetically keyed to make disarming it very difficult and it resets itself automatically.
If you need a pool alarm that cannot be deactivated once it is set in place, than the Poolguard PGRM-2 In-Ground Pool Alarm is the one for you. It must be physically removed from the pool and put into sleep mode to deactivate, which means it is tamper proof even to the point of being stolen, unless you actually know how to deactivate it. It runs on a 9-volt battery, has a 200-foot remote and automatically resets when placed back into the pool. It would have scored higher on the list, but deactivation sometimes causes false alarms, and if you are trying to take a midnight swim in a suburban neighborhood, that will cause problems.
One of the best pool alarms made, the Maytronics International Swim Alert Pool Alarm is highly sensitive and must be mounted correctly to eliminate false alarms. It mounts on the deck and the alarm can be heard up to 100 feet away. The immersion probe must be kept at about 8.5 inches beneath the surface of the water or you may end up with consistent false alarms. That said, when it is set up correctly, it is one of the most sensitive and reliable alarms on the list. It will sound an alarm when some object as little as 18 pounds enters the water, which makes it good for animal protection too.