The identity of a mysterious vessel spotted on the horizon has now been confirmed.

People were baffled as the unidentified craft was pulled westwards by tugs on Thursday (August 1), with many confused by its odd structure.

But The Argus can confirm it was a jack-up rig, which can now be seen berthed at Shoreham Port.

The Argus: A jack-up rig similar to the one in ShorehamA jack-up rig similar to the one in Shoreham (Image: Kees Torn/WikiCommons)

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The rigs are used for marine construction operations and are commonly used to allow work to be carried out at offshore windfarms or oil and gas rigs.

The four legs can be lowered and anchored into the seabed while the platform can raise up or down.

Exactly why the rig is berthed at Shoreham Port has not been confirmed.