The family of 56-year-old Derek Batten, missing skipper of Kaz II, the catamaran found drifting off the Australian coast last week, are convinced that foul play is responsible for his mysterious disappearance.

Derek’s niece Hope Himing said: ‘My mum has a really strong feeling that Des is out somewhere dark and can’t see.’ The families of the three missing men are doing their utmost to make Queensland police restart their search. Convinced that big seas pitched the trio off the yacht, the police suspended their search, believing that they could not have survived.

The 12m (40ft) catamaran was found in the Tasman Sea with fenders out and its engine running, food, plates and cutlery laid on the table and a laptop connected to the internet whirring in the background. Chief pilot of the rescue helicopter Trevor Wison said that the crew’s personal effects were all still on board, commenting: ‘It’s almost like someone has stepped off the boat.’ Weather and sea conditions were believed to have been good throughout the yacht’s voyage from Airlie Beach. The yacht had been purchased from a local man, who told detectives that the crew were planning to sail her back to their home town of Perth. They were to make their first stop in Townsville, about 300km north of Airlie, but they never arrived, and four days later Kaz II was spotted drifting by a surveillance aircraft.

‘If it was bad weather, why would their fishing lines be out?’ asked Hope Himing. ‘Why would their clothes be piled up; if it were that bad that it knocked three experienced sailors off, why wouldn’t they have put on their life jackets? It just doesn’t add up.’ She believes that Kax II was boarded by occupants of another vessel, and points to the fenders being out.

Adding to the mystery, Investigators who examined the cat’s GPS data have said that it had been drifting with the wind and currents since the crew departed Airlie Beach.