On FishingBooker, captains are the ones who set the cancellation policy. Most captains offer a free cancellation policy with individually set advance notice periods (from 24 hours to 60 days). If you cancel your trip within the advance notice period, you are eligible for a full refund; otherwise, you will forfeit the deposit.
Other captains have a "non-refundable" policy, which means you will forfeit the deposit any time you cancel your trip.
You will see a captain's cancellation policy on the charter listing page. To view this information, scroll down to the Policies section of the page.