Hi @Mark5527,
So sorry to hear about your flooding. I would contact the Airbnb support line and explain what happened and ask for their advice. Sometimes they are able to help cancel without penalty depending on the circumstance. I would personally reach out to your guests and explain what happened, apologize to give them as much time as possible to rebook a new location.
Hopefully you may be able to get this dealt with quickly with a water remediation company, dehumidifiers, and for them to find the cause of the flooding.
Let us know how it goes.