No, fleas are not attracted to water, in fact they commonly drown in water and will actively try to avoid it.
Try giving your dog a bath if it is infested with fleas, and see what the fleas do. They will run like crazy to try and get away from the water.
What the fleas are attracted to are the host from which they can obtain a blood meal. They need this blood in order to survive and reproduce.
There are several ways that they can detect the presence of the host. They can feel minute vibrations in the air and ground to detect the movement of a host. They can also detect the presence of carbon dioxide which is indicative of the presence of a potential meal.
The flea in the pupa stage can remain dormant for months and even years until it detects the presence of a host, at which time it will come out of dormancy and search of the blood meal. It has about two weeks to successfully obtain this before it will naturally die.