Also called Bundy Island, this final one in the series is about 1.4km from the shore. Unless you have a power or sailing boat, it's best to pick a calm day and check the forecast before setting out.
Beware that, outside the marked channels, much of the water between the island and the shore is quite shallow, even at high tide. There's a deep channel from the bridge that passes close to the island.
Most of the island is a declared Nature Reserve and off-limits to caches, but the south-western shore is outside that boundary and officially zoned "Recreational Waterway".
The cache is a 12cm long grey plastic tube hanging in a large tree on the side facing away from the water and includes a pencil.
My thanks to lee737 who 3D-printed the containers for this series.