Which preposition to use with lightship

of Occurrences 2%

PUTNAM, GEORGE R. Lighthouses and lightships of the United States.

off Occurrences 2%

The patient lightship off the pier was swinging drearily as we throbbed past into the gust-swept open and set our bows for the unseen coast of France.

towards Occurrences 1%

I pointed away past the Nore Lightship towards a bit of rising ground on the low-lying Sheppey coast.

Which preposition to use with  lightship