All at Sea. Downs Crime Mysteries, #12

Coral Voyager, a large cruise ship, is confronted by a storm just of the north Queensland coast. It finally runs aground just south of Cairns. A massive rescue effort gets underway and all passengers are safely taken by a flotilla of small boats to Cairns. Due to the brilliant seamanship of its captain, the Coral Voyager sustains very little damage except for its steering. Two ocean going tugs arrive from Townsville and the ship is refloated.
As it heads out to sea under tow, two crewmen are found to be missing. After a thorough search of the vessel, the Queensland Police are notified. Chief Inspector "Sarge" Downs and two colleagues board the ship to investigate only to discover that all is not as it seems. They stay with the ship which is towed back to Townsville and try to unravel the clues as to what exactly had taken place.