Te Aumiti / French Pass has the fastest tidal flows in New Zealand, hence the need for a lighthouse and channel beacon.

The pass is a gateway from Tasman Bay / Te Tai-o-Aorere to the Marlborough Sounds, and is a shortcut of about 15 nautical miles (28 km; 17 mi) that is comparatively more comfortable trip than the alternative routes around the top of Stephens Island or through the Stephens Passage between it and Rangitoto ki te Tonga / D'Urville Island, both wild windy waters.

[8] A prudent mariner will time their passage through here to coincide with a change of tidal stream, when counter-currents and whirlpools lessen.

The beacon on the reef emits a white glow every 1.5 seconds (identification F W), with a range of 4 nautical miles (7.4 km; 4.6 mi).

The warning helps to prevent a boat meeting another one coming from the opposite direction, especially as it is not possible to see others approaching when travelling from the north east in time to avoid collision.

It stands at 5 metres (16 ft) high, and at night emits a white glow every 1.5 seconds, with a range of 4 nautical miles (7.4 km; 4.6 mi).

By this time, passenger and mail steamers regularly took a shortcut through the pass, at night, when travelling between Nelson and Wellington.

Neither the lighthouse and its staircase, nor its companion beacon is open to the public; although they can be seen from a boat and there is a good lookout over French Pass a short walk from nearby Elmslie Bay Wharf.