What can I do to keep large amounts of water out of my crawl space?

The first thing you need to do is determine where the water is coming from. You may have a line leak,  it may be from high water table, or it may be coming in from the outside and you just need to extend your downspouts. It is not good to have water standing in your crawl space, and this should be resolved immediately. Sloping the ground near the crawl space so that the water flows away from your house on all sides may be all that’s needed.