Cancellation policies, refunds and what happens when the weather turns.
Every listing uses one of three cancellation policies and says which one. Flexible gives a full refund while at least one full calendar day is left before the trip date, Moderate while at least 5 full days are left, and Strict refunds 50% with at least 7 full days to go, always counted in the boat's local time. Later than that, what you paid online is not refunded, and a balance the captain has not collected yet is not charged.
If the captain calls the trip off because the weather is unsafe, you get everything back, or you move the trip to another day at no extra cost. Cancellation policies has the full rules with examples, and How to cancel a booking shows where the Cancel button is in Trips. If something went wrong on the day, tell us within 24 hours of the trip's start time.