Almost a drive by if you have a suitable vehicle. Could be a bit of a walk if done on foot but various options are possible. No matter how you get there you will be rewarded with a great adventure, some awesome scenery, and hopefully some finds of the other caches you can do along the way.
Tongue Point is a small spit opposite the old Karori lighthouse, which operated from 1915-1996. The new lighthouse sits on the sea terrace above the point. Tongue Point is also a permanent seal colony where you will see seals on any day of the year, and hence is the main stop for the Seal Coast Safari Tour whose distinctive Toyota 4WD's you may encounter. This area of coast from the Owhiro Bay carpark is very popular for those with 4WD's, trail bikes, quad bikes, mountain bikes, and also for walkers. The main destination for those on foot is the closer seal colony at Sinclair Head where seals can be seen during the winter months.
Whilst it is possible to drive to within 50m of the actual cache you will need a "traditional" 4WD vehicle (i.e. chassis based such as Prado, 4runner, Bighorn, Landrover etc) with suitable tyres and be well experienced in off road driving, to do so. The main challenges are getting over Devil's Gate, and the soft sand you will encounter in the later part of the trip. There is a good description of what to expect
here. It is a fairly straight forward and enjoyable ride for anyone on a trail/dirt bike, or a quad bike. All 4WD's with good ground clearance (including RAV's CRV's etc) should have no problem getting as far as Devil's Gate where there is some parking on the side of the track. This would allow you to at least drive the first 3.9 km, and you could walk or mountain bike the rest. The total distance from the Owhiro Bay carpark to Tongue Point is 10.4 km as measured by my GPSr.
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Note: There is no vehicle (including motorbike) access on Sundays which is reserved for walkers/MTB's only.
The cache is a one litre sistema and is hidden on top of the sea terrace behind the point. This will require a short steepish climb from the track along the shore. Please take all due care, keep an eye out for any younger members of your party and choose your route well. The best approach is to climb from the apex of the vehicle track as it curves around at the point.