The conditions for cancelling journeys vary by shipping company. Usually, the journey may only be cancelled at no cost if the right is explicitly stated in the reservation terms. If you wish to cancel the journey, contact the shipping company as soon as possible. If the journey has not been cancelled in a reasonable time in advance, the ticket price will normally not be refunded.
If you are unable to participate in travel by ship due to illness or other unexpected and serious circumstances, you can usually claim a refund of the ticket price. The shipping company must be notified of the obstacle without delay.