It looks, at first glance, like little more than a modest stone cylinder, but its purpose is precise: it is one of three beacons arranged across the harbour entrance, each positioned to guide vessels safely in and out of what is otherwise a tricky approach. Navigation beacons of this kind work as a system, and this one makes little sense without the other two flanking it elsewhere around the harbour.

The tower is circular in plan and tapers gently as it rises, a form that lends it a quiet solidity. Its most distinctive detail sits at the top, where three stepped ashlar courses, ashlar being squared and finely dressed stone, form a capped tier, the lowest course projecting slightly beyond the eaves. The body of the structure is rendered masonry, finished in whitewash, which would have made it readable against the landscape from a vessel at sea. Together, the three beacons in this group functioned as a set of leading marks, a low-technology but reliable system that allowed mariners to align their position and thread a safe passage through the harbour.