When my sister Juliet suggested a cruise on Doubtful Sound I jumped at the chance.

I'd been to the more accessible Milford Sound four years previously on a road trip with my boyfriend, but never made it quite as far south as Doubtful in the south-west corner of New Zealand. Captain Cook is responsible for the unusual name; he first christened it 'Doubtful Harbour' on sighting it from the Tasman Sea, and didn't enter the inlet as he was 'doubtful' it was navigable under sail. Whalers and sealers later named it Doubtful Sound, though technically, it isn't a sound, but a fiord: formed when a glacial valley is filled by rising sea water levels, it is a long, narrow estuary with steep sides. Most areas are only accessible by sea, as the road network is virtually non-existent - as is the human population.

We set off at midday, eating our sarnies as we cruised across the Manapouri lake in the sunshine, passing the famous powerstation. A short while later, we were on a bus on the narrow Wilmot Pass, looking at waterfalls and native trees and getting further away from civilisation by the minute. We crested a hill, and were greeted by our first view of the spectacular fiord ahead.

It was then downhill to the water and onto the Fiordland Navigator, our home for the night. The boat was kitted out for a good 70 people, and we would be fed and watered on board for the next 18 hours. We were escorted to our cabin and chuffed to find we had an extra big one! There's a choice of private accommodation or bunk style sharing. We opted for the cheapest, and landed on our feet! And things only got better as the day went on, with perfect weather, fantastic food, great staff and good company.

We set sail like the intrepid explorers of old. Over the following hours, we cruised all over the sound, going up different remote and hidden arms of the water, sitting in the sunshine, being blown about the deck and gazing at the spectacular scenery - steep cliffs, snowcapped hills and waterfalls. We spotted fur seals, penguins and albatros and sailed with a pod of bottlenose dolphins jumping up and down beside us. We even ventured out into the Tasman Sea, bouncing about on the waves - a lucky experience usually denied due to weather conditions. We kayaked in the sound, feeling very small in the stunning wilderness, going under a huge waterfall and getting drenched. My sister was alone in her decision to swim in the fiord though, freezing as it was!

By the time the sun was setting, we were tucking into a delicious three course meal, sitting in little leather covered booths as we sailed along. A humourous and interesting nature presention followed, after which we lay on the top deck of the boat gazing at the stars - it was so clear and quiet, with little sound - it really did feel very remote.

The next day, we stuffed ourselves with a cooked breakfast and cruised some more as the sun continued to shine, before heading back the way we came. We went with Real Journeys - a definitely recommended and very real experience that brings you close to nature in spectacular and dramatic surroundings.