For a domestic passenger ferry in Korea, plan around three separate checks: your booking, your identity document and the actual sailing status. Korea Maritime Transportation Safety Authority materials describe individual ticket-and-ID checks during boarding, and the authority publishes passenger-ferry safety and real-time service information. The Korea Shipping Association also operates the national passenger-ferry booking site for many routes.
Foreign travelers should carry the passport or other identification accepted by the operator and should not assume a booking confirmation alone is enough to board. The exact accepted foreign-document list was not independently verified across every ferry operator in this review, so if you plan to use a residence card, digital ID or another non-passport document, confirm it with the operator in advance.
Weather, sea conditions, vessel substitution and port operations can affect island services. Recheck the sailing on the day of travel, especially for the last return boat. For small islands, missing the final sailing can mean an unplanned overnight stay. If a route is not shown clearly on one booking site, check the operator or port directly rather than assuming the route does not run.