Lets look at how the water got to the basement and then we can determine as to how to remove eleminate the water from continuing. Many basements flood because they have had water come in from the exterior weather, or they have had some form of pipe burst and come loose in their home. Some times it can be from some other source like a water heater or some other unit in the property that may have malfunctioned. But please be careful when explaining these things to the insurance companies because many of these things may not be covered and knowing what to say is very important.
If you have water in the basement and it has been sitting for a while, you may need to make sure the water hasnt placed mold or mildew to the areas it affected. Normally it doesnt take long for mold or mildew to set once water has set on it. Once you have determined the leak and aware of the problem, then you should reach out to a public adjuster who will then assist you in communicating with the insurance company making sure you are able to be paid the full amount owed to you for the damages done. The water damage from the water can be very dangerous to your health and many of your items in the basement and many times recovering these things are very difficult and time consuming.
It is important to have someone come out immediately to the area of the basement to make sure they can assist you in saving as much as possible and treat the area with caution while making sure the air quality is maintained.