The standard is what you actually know, not what an inspector might later find. If water entered a basement, a sump pump failed, or insurance paid a claim related to water damage, that is the kind of fact a court would expect a seller to disclose rather than stay silent on.
A buyer's own home inspection, typically $400 to $600, will often catch signs of past water intrusion even if it goes undisclosed, so failing to mention it does not usually avoid the issue, it just moves the conversation to after an offer instead of before one, which tends to go worse for the seller.
Honest disclosure paired with an accurate price for the home's real condition protects you legally and still gets the home sold. Get your hand-reviewed valuation from Joel Dyck.