Find the source
The correct response depends on why water is present. A plumbing leak is different from repeated drainage or groundwater intrusion and may require a different trade to correct the underlying source.
Inspect affected materials
Floor framing, subflooring, insulation and stored items may all be exposed to moisture. Conditions should be evaluated rather than assuming the crawl space will simply dry on its own.
Restore after the cause is controlled
Standing water can be removed and wet materials addressed after the source is managed. Longer-term moisture problems may also call for drainage, ventilation or other building-specific corrections.