Two different fears hide in one question. What if I cancel, and what if the weather does? They have different answers, and both are written down before you pay, which is exactly where you want them.
If you cancel
The universal shape: the closer to the date, the less returns, and high season is strictest. Day charters follow the operator's stated terms, shown before you pay. Weekly MYBA contracts print the ladder explicitly, and the 50% at signature structure means real money is committed early, which is why reading the contract guide before signing is not paranoia, it is hygiene. If your plans carry genuine uncertainty, say so at enquiry: flexible dates and areas with deeper fleets lower the odds of ever using the clause.
If the weather cancels a day charter
The rule that matters: when the captain calls off the day for safety, you reschedule or get your money back. That is the standard we hold our listings to, stated in the operator's terms. What the weather rule does not cover is preference: a grey sky with safe seas is a charter day, and often a lovely one, with the boat's shade and a coastline to yourselves. The line between "unsafe" and "not the postcard" belongs to the captain, and it should; it is the judgment you are paying for.
If the weather argues with a week
Weeks almost never cancel for weather; they reroute. The Mediterranean always has a lee shore, and the itinerary flexibility described in the planning guide is the real world insurance: Tuesday's exposed bay becomes Thursday's, the crossing waits a morning, the protected side of the island hosts lunch. A week planned with two fixed points and room to breathe absorbs almost any forecast without losing anything that mattered.
Insurance, briefly
Charter cancellation insurance exists and serious travel policies can cover charter deposits; worth a conversation for expensive peak weeks booked far ahead. We are brokers of boats, not insurance, so take specifics to an insurer; what we will do is state every cancellation term in writing before any money moves, so the policy conversation has real numbers in it.