Have you ever found bees floating in your pool, birdbath other body of water? Have you ever thought "why are bees so attracted to my pool?" It's likely because they are searching for a water source, and your pool happened to be it.
Bees, like many animals, are made up of mostly water. They need to drink water as much as we do. On hot days, worker bees who forage for nectar will stop completely and forage only for water. On those days, it has been estimated that worker bees can bring up to a gallon of water a day into the hive to keep it going.
A large amount of the water they consume comes from nectar, but they need additional water as well. Bees use water to keep their hives cool during the summer by distributing it throughout the hive. They then distribute cool air by fanning their wings, essentially creating their own air conditioning.
So how is water brought into the hive? Worker bees will find a source of water and store it in a special compartment in their stomach to bring it back to the hive. Once there, they transfer it to other bees. This transfer is called trophallaxis.
An interesting fact about the water bees prefer... the more disgusting (in human terms), the better! They seem to prefer mossy, dirty water over clean, fresh from the faucet water. This is why they flock to puddles, swimming pools and leaves covered in water.
If you love bees but prefer to keep them out of your pool (or keep them from drowning in your pool) you can set up a water station for them. Keep in mind that they will remember the site and use it year-round. A good way to do this is by using a bird bath with rocks in it. They will stand on the rocks and be able to reach the water without drowning. To lure the bees to the water source, spike it! Add a tiny bit of chlorine, sugar or oyster shells. If you think "no way I would drink that!" then you are probably on the right track for their water source.