Elizabeth Marina tidal gate broken
The tidal gate at Elizabeth Marina in St Helier has broken, meaning vessels will have to wait more than an hour longer to enter and exit the harbour.
As the tide goes out, the gate should automatically rise to keep water in and boats afloat.
Harbourmaster Barry Goldman said the hydraulic ram which operates the gates has failed and will take a month to repair.
Until then the gates will remain up, curtailing access to the marina.
"What this means is that we need an extra two metres of tide before vessels can enter and exit," he told BBC News.
"The ram is a massive ram. It weighs about 14 tonnes and we have to get it out, shipped back to the UK, repaired, and got back here.
"It's no easy task so it's likely to take a month or more."
Jersey's 12 metre tidal range is one of the largest in the world, making most island harbours inaccessible during low tide.