A "puddle" of water in your crawlspace isn't just a "puddle." It's an indication that there is a bigger problem. Any form of standing water is unhealthy for your home environment as it invites excessive moisture, mold growth, high humidity levels, and even bugs and critters. The mixture of all these things cause unhealthy air that in turn travels up through your home affecting your living space as well as you and your family.
What issues are you seeing?