A multi-million pound project to create a testing platform for wave energy devices in Cornwall has ground to a halt.
Engineers have postponed plans to float the copper cable ashore after it sank, raising fears it could become enmeshed on the seabed.
The cable, which was 650ft (200m) from land on Thursday evening, will now be rewound onto a ship offshore.
Engineers are considering whether to deploy a new flotation device.
The setback is the latest of a series to hit the £42m Wave Hub project over the past week.
Guy Lavender from the Regional Development Agency, which is co-ordinating the project, told BBC News: "It's frustrating and disappointing.
"It could be a few days' time or longer before we try to bring it ashore again."
He admitted the problems were also surprising.
"Copper cable has been laid all over the world using the same methods."
The cable will link wave energy machines off the Cornwall coast with the National Grid.