suggestion,

forced or unforseen detour / itenerary change

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Note added at 46 mins (2016-09-09 17:24:25 GMT)
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" Cruise lines reserve the right to alter itineraries by changing or eliminating ports altogether. If a change is made before sailing, many cruise companies will offer customers an opportunity to cancel and receive a refund or to rebook on a future sailing. But when the ship is forced to change course midcruise, passengers are rarely offered or entitled to any compensation, according to the fine print in the ticket contract. "

A logbook (a ship's logs or simply log) is a record of important events in the management, operation, and navigation of a ship. Details related to the voyage should be recorded, such as courses steered and distances sailed, position fixings, weather and sea conditions, changes to the voyage plan, details of pilots' embarkation/disembarkation, entry into areas covered by, and compliance with, routing schemes or reporting systems.

The following notes give guidance on recording navigational activities based on the requirements of investigation authorities in following up an incident:

4.) Bridge Deck Log - To contain sufficient navigational information to reconstruct a voyage including: the recording of position at regular intervals, alterations of course and speed, weather and sea conditions, precautions taken in restricted visibility or heavy seas, significant navigational events.